计算机专业毕业设计--英文文献(含译文)
计算机 毕业设计 英文资料翻译
计算机毕业设计英文资料翻译青岛理工大学计算机工程学院毕业设计(论文)英文资料翻译题目:A Novel Cross-layer Quality-of-serviceModelFor Mobile AD hoc Network学院: 计算机工程学院专业: 计算机科学与技术姓名:学号:英文资料翻译译文一种新型的移动AD HOC网络跨层服务质量模型分层协议的体系结构只能为移动Ad Hoc网络(简称MANETs )提供部分堆栈。
这给移动Ad Hoc网络中的多媒体通信的质量保证带来了很大的困难。
为了改进移动Ad Hoc网络中的多媒体信息传输的服务质量，本文将介绍一种针对移动Ad Hoc网络的跨层服务质量模型—-CQMM。
CQMM的一个核心组件是网络状态储存库(NSR)，它是信息交换的中心，而且能在堆栈中的不同协议层之间共享。
同时，CQMM能够实现所有标准的QoS 控制。
另外，CQMM还能消除堆栈中不同协议层之间的冗余功能，并有效的执行QoS控制和网络性能的全面改善。
1、引言随着多媒体技术的快速发展，和个人通信带宽的增加，音频和视频服务已开始在MANETs中出现。
与静态网络和因特网不同的是，MANETs中的多媒体通信，如音频和视频服务，它们对QoS的保证有非常严的要求，特别是延迟的保证。
此外，具有不同QoS要求用户之间的通信可以集成服务。
这给MANETs.多媒体通信的QoS保证提出了很大的挑战。
主要有两个原因:1 )MANETs是在一种传统的无线环境下运行的，即，该环境随时间而变化，具有不可靠的物理链接、广播频道和动态的有限的带宽，等等。
因此，它只能为有严格QoS要求的被区分的服务提供有限的能力。
2 )由于MANETs的灵活性，多级跳以及自组性，因而，传统的流动项目和访问控制机制就非常难以实现。
目前，我国大部分基于MANETs传统的多层协议结构的QoS研究都侧重于支持QoS的MAC协议， QoS路由协议和与QoS支持适应的应用层协议，等等。
计算机专业毕业设计说明书外文翻译(中英对照)
Talking about security loopholesRichard S. Kraus reference to the core network security business objective is to protect the sustainability of the system and data security, This two of the main threats come from the worm outbreaks, hacking attacks, denial of service attacks, Trojan horse. Worms, hacker attacks problems and loopholes closely linked to, if there is major security loopholes have emerged, the entire Internet will be faced with a major challenge. While traditional Trojan and little security loopholes, but recently many Trojan are clever use of the IE loophole let you browse the website at unknowingly were on the move.Security loopholes in the definition of a lot, I have here is a popular saying: can be used to stem the "thought" can not do, and are safety-related deficiencies. This shortcoming can be a matter of design, code realization of the problem.Different perspective of security loo phole sIn the classification of a specific procedure is safe from the many loopholes in classification.1. Classification from the user groups:● Public loopholes in the software category. If the loopholes in Windows, IEloophole, and so on.● specialized software loophole. If Oracle loopholes, Apach e, etc. loopholes.2. Data from the perspective include :● could not reasonably be read and read data, including the memory of thedata, documents the data, Users input data, the data in the database, network,data transmission and so on.● designa ted can be written into the designated places (including the localpaper, memory, databases, etc.)● Input data can be implemented (including native implementation,according to Shell code execution, by SQL code execution, etc.)3. From the point of view of the scope of the role are :● Remote loopholes, an attacker could use the network and directly throughthe loopholes in the attack. Such loopholes great harm, an attacker can createa loophole through other people's computers operate. Such loopholes and caneasily lead to worm attacks on Windows.● Local loopholes, the attacker must have the machine premise accesspermissions can be launched to attack the loopholes. Typical of the local authority to upgrade loopholes, loopholes in the Unix system are widespread, allow ordinary users to access the highest administrator privileges.4. Trigger conditions from the point of view can be divided into:● Initiative trigger loopholes, an attacker can take the initiative to use the loopholes in the attack, If direct access to computers.● Passive trigger loopholes must be computer operators can be carried out attacks with the use of the loophole. For example, the attacker made to a mail administrator, with a special jpg image files, if the administrator to open image files will lead to a picture of the software loophole was triggered, thereby system attacks, but if managers do not look at the pictures will not be affected by attacks.5. On an operational perspective can be divided into:● File opera tion type, mainly for the operation of the target file path can be controlled (e.g., parameters, configuration files, environment variables, the symbolic link HEC), this may lead to the following two questions: ◇Content can be written into control, the contents of the documents can be forged. Upgrading or authority to directly alter the important data (such as revising the deposit and lending data), this has many loopholes. If history Oracle TNS LOG document can be designated loopholes, could lead to any person may control the operation of the Oracle computer services;◇information content can be output Print content has been contained to a screen to record readable log files can be generated by the core users reading papers, Such loopholes in the history of the Unix system crontab subsystem seen many times, ordinary users can read the shadow ofprotected documents;● Memory coverage, mainly for memory modules can be specified, writecontent may designate such persons will be able to attack to enforce the code (buffer overflow, format string loopholes, PTrace loopholes, Windows 2000 history of the hardware debugging registers users can write loopholes), or directly alter the memory of secrets data.● logic errors, such wide gaps exist, but very few changes, so it is difficult todiscern, can be broken down as follows : ◇loopholes competitive conditions (usually for the design, typical of Ptrace loopholes, The existence of widespread document timing of competition) ◇wrong tactic, usually in design. If the history of the FreeBSD Smart IO loopholes. ◇Algorithm (usually code or design to achieve), If the history of Microsoft Windows 95/98 sharing password can easily access loopholes. ◇Imperfections of the design, such as TCP / IP protocol of the three-step handshake SYN FLOOD led to a denial of service attack. ◇realize the mistakes (usually no problem for the design, but the presence of coding logic wrong, If history betting system pseudo-random algorithm)● External orders, Typical of external commands can be controlled (via the PATH variable, SHELL importation of special characters, etc.) and SQL injection issues.6. From time series can be divided into:● has long found loopholes: manufacturers already issued a patch or repairmethods many people know already. Such loopholes are usually a lot of people have had to repair macro perspective harm rather small.● recently discovered loophole: manufacturers just made patch or repairmethods, the people still do not know more. Compared to greater danger loopholes, if the worm appeared fool or the use of procedures, so will result in a large number of systems have been attacked.● 0day: not open the loophole in the private transactions. Usually such loopholes to the public will not have any impact, but it will allow an attacker to the targetby aiming precision attacks, harm is very great.Different perspective on the use of the loopholesIf a defect should not be used to stem the "original" can not do what the (safety-related), one would not be called security vulnerability, security loopholes and gaps inevitably closely linked to use.Perspective use of the loopholes is:● Data Perspective: visit had not visited the data, including reading and writing.This is usually an attacker's core purpose, but can cause very serious disaster (such as banking data can be written).● Competence Perspective: Major Powers to bypass or p ermissions. Permissionsare usually in order to obtain the desired data manipulation capabilities.● Usability perspective: access to certain services on the system of controlauthority, this may lead to some important services to stop attacks and lead to a denial of service attack.● Authentication bypass: usually use certification system and the loopholes willnot authorize to access. Authentication is usually bypassed for permissions or direct data access services.● Code execution perspective: mainly procedures for the importation of thecontents as to implement the code, obtain remote system access permissions or local system of higher authority. This angle is SQL injection, memory type games pointer loopholes (buffer overflow, format string, Plastic overflow etc.), the main driving. This angle is usually bypassing the authentication system, permissions, and data preparation for the reading.Loopholes explore methods mustFirst remove security vulnerabilities in software BUG in a subset, all software testing tools have security loopholes to explore practical. Now that the "hackers" used to explore the various loopholes that there are means available to the model are:● fuzz testing (black box testing), by constructing procedures may lead toproblems of structural input data for automatic testing.● FOSS audit (White Box), now have a series of tools that can assist in thedetection of the safety procedures BUG. The most simple is your hands the latest version of the C language compiler.● IDA anti-compilation of the audit (gray box testing), and above the sourceaudit are very similar. The only difference is that many times you can obtain software, but you can not get to the source code audit, But IDA is a very powerful anti-Series platform, let you based on the code (the source code is in fact equivalent) conducted a safety audit.● dynamic tracking, is the record of proceedings under different conditions andthe implementation of all security issues related to the operation (such as file operations), then sequence analysis of these operations if there are problems, it is competitive category loopholes found one of the major ways. Other tracking tainted spread also belongs to this category.● patch, the software manufacturers out of the question usually addressed in thepatch. By comparing the patch before and after the source document (or the anti-coding) to be aware of the specific details of loopholes.More tools with which both relate to a crucial point: Artificial need to find a comprehensive analysis of the flow path coverage. Analysis methods varied analysis and design documents, source code analysis, analysis of the anti-code compilation, dynamic debugging procedures.Grading loopholesloopholes in the inspection harm should close the loopholes and the use of the hazards related Often people are not aware of all the Buffer Overflow Vulnerability loopholes are high-risk. A long-distance loophole example and better delineation:●R emote access can be an OS, application procedures, version information.●open unnecessary or dangerous in the service, remote access to sensitiveinformation systems.● Remote can be restricted for the documents, data reading.●remotely important or res tricted documents, data reading.● may be limited for long-range document, data revisions.● Remote can be restricted for important documents, data changes.● Remote can be conducted without limitation in the important documents, datachanges, or for general service denial of service attacks.● Remotely as a normal user or executing orders for system and network-leveldenial of service attacks.● may be remote management of user identities to the enforcement of the order(limited, it is not easy to use).● can be remote management of user identities to the enforcement of the order(not restricted, accessible).Almost all local loopholes lead to code execution, classified above the 10 points system for:●initiative remote trigger code execution (such a s IE loophole).● passive trigger remote code execution (such as Word gaps / charting softwareloopholes).DEMOa firewall segregation (peacekeeping operation only allows the Department of visits) networks were operating a Unix server; operating systems only root users and users may oracle landing operating system running Apache (nobody authority), Oracle (oracle user rights) services.An attacker's purpose is to amend the Oracle database table billing data. Its possible attacks steps:● 1. Access pea cekeeping operation of the network. Access to a peacekeepingoperation of the IP address in order to visit through the firewall to protect the UNIX server.● 2. Apache services using a Remote Buffer Overflow Vulnerability direct accessto a nobody's competence hell visit.● 3. Using a certain operating system suid procedure of the loophole to upgradetheir competence to root privileges.● 4. Oracle sysdba landing into the database (local landing without a password).● 5. Revised target table data.Over five down for process analysis:●Step 1: Authentication bypass●Step 2: Remote loopholes code execution (native), Authentication bypassing ● Step 3: permissions, authentication bypass● Step 4: Authentication bypass● Step 5: write data安全漏洞杂谈Richard S. Kraus 网络安全的核心目标是保障业务系统的可持续性和数据的安全性，而这两点的主要威胁来自于蠕虫的暴发、黑客的攻击、拒绝服务攻击、木马。
计算机专业文献翻译
毕业设计（论文）外文资料原文及译文原文出处：《Cloud Computing》作者：M ichael Miller以下为英文原文Beyond the Desktop: An Introduction to Cloud ComputingIn a world that sees new technological trends bloom and fade on almost a daily basis, one new trend promises more longevity. This trend is called cloud computing, and it will change the way you use your computer and the Internet.Cloud computing portends a major change in how we store information and run applications. Instead of running programs and data on an individual desktop computer, everything is hosted in the “cloud”—a nebulous assemblage of computers and servers accessed via the Internet. Cloud computing lets you access all your applications and documents from anywhere in the world, freeing you from the confines of the desktop and making it easier for group members in different locations to collaborate.The emergence of cloud computing is the computing equivalent of the electricity revolution of a century ago. Before the advent of electrical utilities, every farm and business produced its own electricity from freestanding generators. After the electrical grid was created, farms and businesses shut down their generators and bought electricity from the utilities, at a much lower price (and with much greater reliability) than they could produce on their own.Look for the same type of revolution to occur as cloud computing takes hold. Thedesktop-centric notion of computing that we hold today is bound to fall by the wayside as we come to expect the universal access, 24/7 reliability, and ubiquitous collaboration promised by cloud computing.It is the way of the future.Cloud Computing: What It Is—and What It Isn’tWith traditional desktop computing, you run copies of software programs on each computer you own. The documents you create are stored on the computer on which they were created. Although documents can be accessed from other computers on the network, they can’t be accessed by computers outside the network.The whole scene is PC-centric.With cloud computing, the software programs you use aren’t run from your personal computer, but are rather stored on servers accessed via the Internet. If your computer crashes, the software is still available for others to use. Same goes for the documents you create; they’re stored on a collection of servers accessed via the Internet. Anyone with permission can not only access the documents, but can also edit and collaborate on those documents in real time. Unlike traditional computing, this cloud computing model isn’t PC-centric, it’sdocument-centric. Which PC you use to access a document simply isn’t important.But that’s a simplification. Let’s look in more detail at what cloud computing is—and, just as important, what it isn’t.What Cloud Computing Isn’tFirst, cloud computing isn’t network computing. With network computing,applications/documents are hosted on a single company’s server and accessed over the company’s network. Cloud computing is a lot bigger than that. It encompasses multiple companies, multiple servers, and multiple networks. Plus, unlike network computing, cloud services and storage are accessible from anywhere in the world over an Internet connection; with network computing, access is over the company’s network only.Cloud computing also isn’t traditional outsourcing, where a company farms out (subcontracts) its computing services to an outside firm. While an outsourcing firm might host a company’s data or applications, those documents and programs are only accessible to the company’s employees via the company’s network, not to the entire world via the Internet.So, despite superficial similarities, networking computing and outsourcing are not cloud computing.What Cloud Computing IsKey to the definition of cloud computing is the “cloud”itself. For our purposes, the cloud is a large group of interconnected computers. These computers can be personal computers or network servers; they can be public or private. For example, Google hosts a cloud that consists of both smallish PCs and larger servers. Google’s cloud is a private one (that is, Google owns it) that is publicly accessible (by Google’s users).This cloud of computers extends beyond a single company or enterprise. The applications and data served by the cloud are available to broad group of users, cross-enterprise andcross-platform. Access is via the Internet. Any authorized user can access these docs and apps from any computer over any Internet connection. And, to the user, the technology and infrastructure behind the cloud is invisible. It isn’t apparent (and, in most cases doesn’t matter) whether cloud services are based on HTTP, HTML, XML, JavaScript, or other specific technologies.It might help to examine how one of the pioneers of cloud computing, Google, perceives the topic. From Google’s perspective, there are six key properties of cloud computing:·Cloud computing is user-centric.Once you as a user are connected to the cloud, whatever is stored there—documents, messages, images, applications, whatever—becomes yours. In addition, not only is the data yours, but you can also share it with others. In effect, any device that accesses your data in the cloud also becomes yours.·Cloud computing is task-centric.Instead of focusing on the application and what it can do, the focus is on what you need done and how the application can do it for you., Traditional applications—word processing, spreadsheets, email, and so on—are becoming less important than the documents they create.·Cloud computing is powerful. Connecting hundreds or thousands of computers together in a cloud creates a wealth of computing power impossible with a single desktop PC. ·Cloud computing is accessible. Because data is stored in the cloud, users can instantly retrieve more information from multiple repositories. You’re not limited to a single source of data, as you are with a desktop PC.·Cloud computing is intelligent. With all the various data stored on the computers in a cloud, data mining and analysis are necessary to access that information in an intelligent manner.·Cloud computing is programmable.Many of the tasks necessary with cloud computing must be automated. For example, to protect the integrity of the data, information stored on a single computer in the cloud must be replicated on other computers in the cloud. If that one computer goes offline, the cloud’s programming automatically redistributes that computer’s data to a new computer in the cloud.All these definitions behind us, what constitutes cloud computing in the real world?As you’ll learn throughout this book, a raft of web-hosted, Internet-accessible,group-collaborative applications are currently available, with many more on the way. Perhaps the best and most popular examples of cloud computing applications today are the Google family of applications—Google Docs & Spreadsheets, Google Calendar, Gmail, Picasa, and the like. All of these applications are hosted on Google’s servers, are accessible to any user with an Internet connection, and can be used for group collaboration from anywhere in the world.In short, cloud computing enables a shift from the computer to the user, from applications to tasks, and from isolated data to data that can be accessed from anywhere and shared with anyone. The user no longer has to take on the task of data management; he doesn’t even have to remember where the data is. All that matters is that the data is in the cloud, and thus immediately available to that user and to other authorized users.From Collaboration to the Cloud: A Short History of CloudComputingCloud computing has as its antecedents both client/server computing and peer-to-peer distributed computing. It’s all a matter of how centralized storage facilitates collaboration and how multiple computers work together to increase computing power.Client/Server Computing: Centralized Applications and StorageIn the antediluvian days of computing (pre-1980 or so), everything operated on the client/server model. All the software applications, all the data, and all the control resided on huge mainframe computers, otherwise known as servers. If a user wanted to access specific data or run a program, he had to connect to the mainframe, gain appropriate access, and then do his business while essentially “renting”the program or data from the server.Users connected to the server via a computer terminal, sometimes called a workstation or client. This computer was sometimes called a dumb terminal because it didn’t have a lot (if any!) memory, storage space, or processing power. It was merely a device that connected the user to and enabled him to use the mainframe computer.Users accessed the mainframe only when granted permission, and the information technology (IT) staff weren’t in the habit of handing out access casually. Even on a mainframe computer, processing power is limited—and the IT staff were the guardians of that power. Access was not immediate, nor could two users access the same data at the same time.Beyond that, users pretty much had to take whatever the IT staff gave them—with no variations. Want to customize a report to show only a subset of the normal information? Can’t do it. Want to create a new report to look at some new data? You can’t do it, although the IT staff can—but on their schedule, which might be weeks from now.The fact is, when multiple people are sharing a single computer, even if that computer is a huge mainframe, you have to wait your turn. Need to rerun a financial report? No problem—if you don’t mind waiting until this afternoon, or tomorrow morning. There isn’t always immediate access in a client/server environment, and seldom is there immediate gratification.So the client/server model, while providing similar centralized storage, differed from cloud computing in that it did not have a user-centric focus; with client/server computing, all the control rested with the mainframe—and with the guardians of that single computer. It was not a user-enabling environment.Peer-to-Peer Computing: Sharing ResourcesAs you can imagine, accessing a client/server system was kind of a “hurry up and wait”experience. The server part of the system also created a huge bottleneck. All communications between computers had to go through the server first, however inefficient that might be.The obvious need to connect one computer to another without first hitting the server led to the development of peer-to-peer (P2P) computing. P2P computing defines a network architecture inwhich each computer has equivalent capabilities and responsibilities. This is in contrast to the traditional client/server network architecture, in which one or more computers are dedicated to serving the others. (This relationship is sometimes characterized as a master/slave relationship, with the central server as the master and the client computer as the slave.)P2P was an equalizing concept. In the P2P environment, every computer is a client and a server; there are no masters and slaves. By recognizing all computers on the network as peers, P2P enables direct exchange of resources and services. There is no need for a central server, because any computer can function in that capacity when called on to do so.P2P was also a decentralizing concept. Control is decentralized, with all computers functioning as equals. Content is also dispersed among the various peer computers. No centralized server is assigned to host the available resources and services.Perhaps the most notable implementation of P2P computing is the Internet. Many of today’s users forget (or never knew) that the Internet was initially conceived, under its original ARPAnet guise, as a peer-to-peer system that would share computing resources across the United States. The various ARPAnet sites—and there weren’t many of them—were connected together not as clients and servers, but as equals.The P2P nature of the early Internet was best exemplified by the Usenet network. Usenet, which was created back in 1979, was a network of computers (accessed via the Internet), each of which hosted the entire contents of the network. Messages were propagated between the peer computers; users connecting to any single Usenet server had access to all (or substantially all) the messages posted to each individual server. Although the users’connection to the Usenet server was of the traditional client/server nature, the relationship between the Usenet servers was definitely P2P—and presaged the cloud computing of today.That said, not every part of the Internet is P2P in nature. With the development of the World Wide Web came a shift away from P2P back to the client/server model. On the web, each website is served up by a group of computers, and sites’visitors use client software (web browsers) to access it. Almost all content is centralized, all control is centralized, and the clients have no autonomy or control in the process.Distributed Computing: Providing More Computing PowerOne of the most important subsets of the P2P model is that of distributed computing, where idle PCs across a network or across the Internet are tapped to provide computing power for large, processor-intensive projects. It’s a simple concept, all about cycle sharing between multiple computers.A personal computer, running full-out 24 hours a day, 7 days a week, is capable of tremendous computing power. Most people don’t use their computers 24/7, however, so a good portion of a computer’s resources go unused. Distributed computing uses those resources.When a computer is enlisted for a distributed computing project, software is installed on the machine to run various processing activities during those periods when the PC is typically unused. The results of that spare-time processing are periodically uploaded to the distributedcomputing network, and combined with similar results from other PCs in the project. The result, if enough computers are involved, simulates the processing power of much larger mainframes and supercomputers—which is necessary for some very large and complex computing projects.For example, genetic research requires vast amounts of computing power. Left to traditional means, it might take years to solve essential mathematical problems. By connecting together thousands (or millions) of individual PCs, more power is applied to the problem, and the results are obtained that much sooner.Distributed computing dates back to 1973, when multiple computers were networked togetherat the Xerox PARC labs and worm software was developed to cruise through the network looking for idle resources. A more practical application of distributed computing appeared in 1988, when researchers at the DEC (Digital Equipment Corporation) System Research Center developed software that distributed the work to factor large numbers among workstations within their laboratory. By 1990, a group of about 100 users, utilizing this software, had factored a 100-digit number. By 1995, this same effort had been expanded to the web to factor a 130-digit number.It wasn’t long before distributed computing hit the Internet. The first major Internet-based distributed computing project was , launched in 1997, which employed thousands of personal computers to crack encryption codes. Even bigger was SETI@home, launched in May 1999, which linked together millions of individual computers to search for intelligent life in outer space.Many distributed computing projects are conducted within large enterprises, using traditional network connections to form the distributed computing network. Other, larger, projects utilize the computers of everyday Internet users, with the computing typically taking place offline, and then uploaded once a day via traditional consumer Internet connections.Collaborative Computing: Working as a GroupFrom the early days of client/server computing through the evolution of P2P, there has been a desire for multiple users to work simultaneously on the same computer-based project. This type of collaborative computing is the driving force behind cloud computing, but has been aroundfor more than a decade.Early group collaboration was enabled by the combination of several different P2P technologies. The goal was (and is) to enable multiple users to collaborate on group projects online, in real time.To collaborate on any project, users must first be able to talk to one another. In today’s environment, this means instant messaging for text-based communication, with optionalaudio/telephony and video capabilities for voice and picture communication. Most collaboration systems offer the complete range of audio/video options, for full-featured multiple-user video conferencing.In addition, users must be able to share files and have multiple users work on the same document simultaneously. Real-time whiteboarding is also common, especially in corporate andeducation environments.Early group collaboration systems ranged from the relatively simple (Lotus Notes and Microsoft NetMeeting) to the extremely complex (the building-block architecture of the Groove Networks system). Most were targeted at large corporations, and limited to operation over the companies’private networks.Cloud Computing: The Next Step in CollaborationWith the growth of the Internet, there was no need to limit group collaboration to asingle enterprise’s network environment. Users from multiple locations within a corporation, and from multiple organizations, desired to collaborate on projects that crossed company and geographic boundaries. To do this, projects had to be housed in the “cloud”of the Internet, and accessed from any Internet-enabled location.The concept of cloud-based documents and services took wing with the development of large server farms, such as those run by Google and other search companies. Google already had a collection of servers that it used to power its massive search engine; why not use that same computing power to drive a collection of web-based applications—and, in the process, provide a new level of Internet-based group collaboration?That’s exactly what happened, although Google wasn’t the only company offering cloud computing solutions. On the infrastructure side, IBM, Sun Systems, and other big iron providers are offering the hardware necessary to build cloud networks. On the software side, dozens of companies are developing cloud-based applications and storage services.Today, people are using cloud services and storage to create, share, find, and organize information of all different types. Tomorrow, this functionality will be available not only to computer users, but to users of any device that connects to the Internet—mobile phones, portable music players, even automobiles and home television sets.The Network Is the Computer: How Cloud Computing WorksSun Microsystems’s slogan is “The network is the computer,”and that’s as good as any to describe how cloud computing works. In essence, a network of computers functions as a single computer to serve data and applications to users over the Internet. The network exists in the “cloud”of IP addresses that we know as the Internet, offers massive computing power and storage capability, and enables widescale group collaboration.But that’s the simple explanation. Let’s take a look at how cloud computing works in more detail.Understanding Cloud ArchitectureThe key to cloud computing is the “cloud”—a massive network of servers or even individual PCs interconnected in a grid. These computers run in parallel, combining the resources of eachto generate supercomputing-like power.What, exactly, is the “cloud”? Put simply, the cloud is a collection of computers and servers that are publicly accessible via the Internet. This hardware is typically owned and operated by a third party on a consolidated basis in one or more data center locations. The machines can run any combination of operating systems; it’s the processing power of the machines that matter, not what their desktops look like.As shown in Figure 1.1, individual users connect to the cloud from their own personal computers or portable devices, over the Internet. To these individual users, the cloud is seen as a single application, device, or document. The hardware in the cloud (and the operating system that manages the hardware connections) is invisible.FIGURE 1.1How users connect to the cloud.This cloud architecture is deceptively simple, although it does require some intelligent management to connect all those computers together and assign task processing to multitudes of users. As you can see in Figure 1.2, it all starts with the front-end interface seen by individual users. This is how users select a task or service (either starting an application or opening a document). The user’s request then gets passed to the system management, which finds the correct resources and then calls the system’s appropriate provisioning services. These services carve out the necessary resources in the cloud, launch the appropriate web application, and either creates or opens the requested document. After the web application is launched, the system’s monitoring and metering functions track the usage of the cloud so that resources are apportioned and attributed to the proper user(s).FIGURE 1.2The architecture behind a cloud computing system.As you can see, key to the notion of cloud computing is the automation of many management tasks. The system isn’t a cloud if it requires human management to allocate processes to resources. What you have in this instance is merely a twenty-first-century version ofold-fashioned data center–based client/server computing. For the system to attain cloud status, manual management must be replaced by automated processes.Understanding Cloud StorageOne of the primary uses of cloud computing is for data storage. With cloudstorage, data is stored on multiple third-party servers, rather than on the dedicated servers used in traditional networked data storage.When storing data, the user sees a virtual server—that is, it appears as if the data is stored in a particular place with a specific name. But that place doesn’t exist in reality. It’s just a pseudonym used to reference virtual space carved out of the cloud. In reality, the user’s data could be stored on any one or more of the computers used to create the cloud. The actual storage location may even differ from day to day or even minute to minute, as the cloud dynamically manages available storage space. But even though the location is virtual, the user sees a “static”location for his data—and can actually manage his storage space as if it were connected to his own PC.Cloud storage has both financial and security-associated advantages.Financially, virtual resources in the cloud are typically cheaper than dedicated physical resources connected to a personal computer or network. As for security, data stored in the cloud is secure from accidental erasure or hardware crashes, because it is duplicated across multiple physical machines; since multiple copies of the data are kept continually, the cloud continues to function as normal even if one or more machines go offline. If one machine crashes, the data is duplicated on other machines in the cloud.Understanding Cloud ServicesAny web-based application or service offered via cloud computing is called a cloud service. Cloud services can include anything from calendar and contact applications to word processing and presentations. Almost all large computing companies today, from Google to Amazon to Microsoft, are developing various types of cloud services.With a cloud service, the application itself is hosted in the cloud. An individual user runs the application over the Internet, typically within a web browser. The browser accesses the cloud service and an instance of the application is opened within the browser window. Once launched, the web-based application operates and behaves like a standard desktop application. The only difference is that the application and the working documents remain on the host’s cloud servers.Cloud services offer many advantages. If the user’s PC crashes, it doesn’t affect either the host application or the open document; both remain unaffected in the cloud. In addition, an individual user can access his applications and documents from any location on any PC. He doesn’t have to have a copy of every app and file with him when he moves from office to home to remote location. Finally, because documents are hosted in the cloud, multiple users can collaborate on the same document in real time, using any available Internet connection. Documents are no longer machine-centric. Instead, they’re always available to any authorized user.Companies in the Cloud: Cloud Computing TodayWe’re currently in the early days of the cloud computing revolution. Although many cloud services are available today, more and more interesting applications are still in development. That said, cloud computing today is attracting the best and biggest companies from across the computing industry, all of whom hope to establish profitable business models based in the cloud.As discussed earlier in this chapter, perhaps the most noticeable company currently embracing the cloud computing model is Google. As you’ll see throughout this book, Google offers a powerful collection of web-based applications, all served via its cloud architecture. Whether you want cloud-based word processing (Google Docs), presentation software (Google Presentations), email (Gmail), or calendar/scheduling functionality (Google Calendar), Google has an offering. And best of all, Google is adept in getting all of its web-based applications to interface with each other; their cloud services are interconnected to the user’s benefit.Other major companies are also involved in the development of cloud services. Microsoft, for example, offers its Windows Live suite of web-based applications, as well as the Live Mesh initiative that promises to link together all types of devices, data, and applications in a common cloud-based platform. Amazon has its Elastic Compute Cloud (EC2), a web service that provides cloud-based resizable computing capacity for application developers. IBM has established a Cloud Computing Center to deliver cloud services and research to clients. And numerous smaller companies have launched their own webbased applications, primarily (but not exclusively) to exploit the collaborative nature of cloud services.As we work through this book, we’ll examine many of these companies and their offerings. All you need to know for now is that there’s a big future in cloud computing—and everybody’s jumping on the bandwagon.Why Cloud Computing MattersWhy is cloud computing important? There are many implications of cloud technology, for both developers and end users.For developers, cloud computing provides increased amounts of storage and processing power to run the applications they develop. Cloud computing also enables new ways to access information, process and analyze data, and connect people and resources from any location anywhere in the world. In essence, it takes the lid off the box; with cloud computing, developers are no longer boxed in by physical constraints.For end users, cloud computing offers all those benefits and more. A person using a web-based application isn’t physically bound to a single PC, location, or network. His applications and documents can be accessed wherever he is, whenever he wants. Gone is the fear of losing data if a computer crashes. Documents hosted in the cloud always exist, no matter what happens to the user’s machine. And then there’s the benefit of group collaboration. Users from around the world can collaborate on the same documents, applications, and projects, in real time. It’s a whole new world of collaborative computing, all enabled by the notion of cloud computing.And cloud computing does all this at lower costs, because the cloud enables more efficient sharing of resources than does traditional network computing. With cloud computing, hardware doesn’t have to be physically adjacent to a firm’s office or data center. Cloud infrastructure can be located anywhere, including and especially areas with lower real estate and electricity costs. Inaddition, IT departments don’t have to engineer for peak-load capacity, because the peak load can be spread out among the external assets in the cloud. And, because additional cloud resources are always at the ready, companies no longer have to purchase assets for infrequent intensive computing tasks. If you need more processing power, it’ s always there in the cloud—and accessible on a cost-efficient basis.。
计算机类毕业设计英文文献及翻译
外貌在环境面板上的共同标签部分包括光，云，太阳和月亮的控制器。
启用灯光--当设置后，环境面板被点亮并且物体的场景会在全天不断变化。
当此复选框被清除，在场景中所有对象不亮也不随着一天时间的变化而变化。
（该对象将仍然被视为未点亮时，他们将使用为他们定制的颜色，材料和正常的价值观）。
启用云--当设置后，一个云层的场景便设置其中。
道路工具将定出海拔类型和云层类型。
默认情况下，此值未设置。
启用太阳/月亮--当设置，太阳和月球环境的效果显示并且月亮环境的效果有助于现场场景内的任何物体的照明。
当此复选框被清除，太阳和月亮不会被显示并且月亮助手停止现场照明。
默认情况下，太阳和月亮是没有设置。
注：太阳和月亮在天空的位置和绘制使用星历模型。
太阳和月亮的位置是根据一天中的时间，日期，纬度和经度绘制的。
月亮的月球阶段也以同样的方式计算。
天空颜色在环境面板上的共同标签部分包括天空的颜色，云的颜色，周围的颜色，天气的控制，和雾。
注：彩色按钮旁边的天空，云，和环境（背景）显示你当前的颜色。
单击每个按钮来改变颜色。
云的颜色--这个颜色的按钮显示您的云层的颜色。
点击就显示颜色对话框，然后选择一个新的颜色，然后点击确定。
环境光颜色--这个颜色的彩色按钮显示您当前的周围灯光组件的颜色。
点击就显示颜色对话框，然后选择一个新的颜色，然后点击确定。
环境光元件有助于场景和物体的亮度；默认设置是应用一个小环境光线。
环境光照亮了现场或对象，当一天的时间设置为晚，对象将仍然由于环境光而可见。
环境光可以用来照亮一个带有黑暗纹理或者用IRIX电脑做出纹理的物体。
（IRIX电脑相对于WINDOWS电脑使用了不同的GAMMA设置，他使Irix计算机处理的纹理总是看上去黑暗，直到图像编辑程序纠正才能恢复正常。
）天气--此选项不使用这种版本的路径工具。
在今后的版本中，天气列表将包含环境设置预设模拟不同时间的天气事件，如日出，上午，傍晚，夜间，多云，雨，雪等。
计算机专业毕业外文翻译原文+封面+中文翻译
本科毕业论文外文翻译外文译文题目（中文）：具体数学：汉诺塔问题学院: 计算机科学与技术专业: 计算机科学与技术学号:学生姓名:指导教师:日期: 二○一二年六月1 Recurrent ProblemsTHIS CHAPTER EXPLORES three sample problems that give a feel for what’s to c ome. They have two traits in common: They’ve all been investigated repeatedly by mathe maticians; and their solutions all use the idea of recurrence, in which the solution to eac h problem depends on the solutions to smaller instances of the same problem.1.1 THE TOWER OF HANOILet’s look first at a neat little puzzle called the Tower of Hanoi,invented by the Fr ench mathematician Edouard Lucas in 1883. We are given a tower of eight disks, initiall y stacked in decreasing size on one of three pegs:The objective is to transfer the entire tower to one of the other pegs, movingonly one disk at a time and never moving a larger one onto a smaller.Lucas furnished his toy with a romantic legend about a much larger Tower of Brah ma, which supposedly has 64 disks of pure gold resting on three diamond needles. At th e beginning of time, he said, God placed these golden disks on the first needle and orda ined that a group of priests should transfer them to the third, according to the rules abov e. The priests reportedly work day and night at their task. When they finish, the Tower will crumble and the world will end.It's not immediately obvious that the puzzle has a solution, but a little thought (or h aving seen the problem before) convinces us that it does. Now the question arises：What' s the best we can do？That is，how many moves are necessary and suff i cient to perfor m the task?The best way to tackle a question like this is to generalize it a bit. The Tower of Brahma has 64 disks and the Tower of Hanoi has 8；let's consider what happens if ther e are TL disks.One advantage of this generalization is that we can scale the problem down even m ore. In fact, we'll see repeatedly in this book that it's advantageous to LOOK AT SMAL L CASES first. It's easy to see how to transfer a tower that contains only one or two di sks. And a small amount of experimentation shows how to transfer a tower of three.The next step in solving the problem is to introduce appropriate notation：NAME ANO CONQUER. Let's say that T n is the minimum number of moves that will t ransfer n disks from one peg to another under Lucas's rules. Then T1is obviously 1 , an d T2= 3.We can also get another piece of data for free, by considering the smallest case of all：Clearly T0= 0，because no moves at all are needed to transfer a tower of n = 0 disks! Smart mathematicians are not ashamed to think small,because general patterns are easier to perceive when the extreme cases are well understood(even when they are trivial).But now let's change our perspective and try to think big；how can we transfer a la rge tower? Experiments with three disks show that the winning idea is to transfer the top two disks to the middle peg, then move the third, then bring the other two onto it. Thi s gives us a clue for transferring n disks in general：We first transfer the n−1 smallest t o a different peg (requiring T n-1moves), then move the largest (requiring one move), and finally transfer the n−1 smallest back onto the largest (req uiring another T n-1moves). Th us we can transfer n disks (for n > 0)in at most 2T n-1+1 moves：T n≤2T n—1+1，for n > 0.This formula uses '≤' instead of '=' because our construction proves only that 2T n—1+1 mo ves suffice; we haven't shown that 2T n—1+1 moves are necessary. A clever person might be able to think of a shortcut.But is there a better way? Actually no. At some point we must move the largest d isk. When we do, the n−1 smallest must be on a single peg, and it has taken at least T moves to put them there. We might move the largest disk more than once, if we're n n−1ot too alert. But after moving the largest disk for the last time, we must trans fr the n−1 smallest disks (which must again be on a single peg)back onto the largest；this too re quires T n−1moves. HenceT n≥ 2T n—1+1，for n > 0.These two inequalities, together with the trivial solution for n = 0, yieldT0=0；T n=2T n—1+1 , for n > 0. (1.1)(Notice that these formulas are consistent with the known values T1= 1 and T2= 3. Our experience with small cases has not only helped us to discover a general formula, it has also provided a convenient way to check that we haven't made a foolish error. Such che cks will be especially valuable when we get into more complicated maneuvers in later ch apters.)A set of equalities like (1.1) is called a recurrence (a. k. a. recurrence relation or r ecursion relation). It gives a boundary value and an equation for the general value in ter ms of earlier ones. Sometimes we refer to the general equation alone as a recurrence, alt hough technically it needs a boundary value to be complete.The recurrence allows us to compute T n for any n we like. But nobody really like to co m pute fro m a recurrence，when n is large；it takes too long. The recurrence only gives indirect, "local" information. A solution to the recurrence would make us much h appier. That is, we'd like a nice, neat, "closed form" for Tn that lets us compute it quic kly，even for large n. With a closed form, we can understand what T n really is.So how do we solve a recurrence? One way is to guess the correct solution,then to prove that our guess is correct. And our best hope for guessing the solution is t o look (again) at small cases. So we compute, successively,T3= 2×3+1= 7; T4= 2×7+1= 15; T5= 2×15+1= 31; T6= 2×31+1= 63.Aha! It certainly looks as ifTn = 2n−1，for n≥0. (1.2)At least this works for n≤6.Mathematical induction is a general way to prove that some statement aboutthe integer n is true for all n≥n0. First we prove the statement when n has its smallest v alue,no; this is called the basis. Then we prove the statement for n > n0,assuming that it has already been proved for all values between n0and n−1, inclusive; this is called th e induction. Such a proof gives infinitely many results with only a finite amount of wo rk.Recurrences are ideally set up for mathematical induction. In our case, for exampl e，(1.2) follows easily from (1.1)：The basis is trivial，since T0 = 20−1= 0.And the indu ction follows for n > 0 if we assume that (1.2) holds when n is replaced by n−1：T n= 2T n+1= 2(2n−1−1)+1=2n−1.Hence (1.2) holds for n as well. Good! Our quest for T n has ended successfully.Of course the priests' task hasn't ended；they're still dutifully moving disks,and wil l be for a while, because for n = 64 there are 264−1 moves (about 18 quintillion). Even at the impossible rate of one move per microsecond, they will need more than 5000 cent uries to transfer the Tower of Brahma. Lucas's original puzzle is a bit more practical, It requires 28−1 = 255 moves, which takes about four minutes for the quick of hand.The Tower of Hanoi recurrence is typical of many that arise in applications of all kinds. In finding a closed-form expression for some quantity of interest like T n we go t hrough three stages：1 Look at small cases. This gives us insight into the problem and helps us in stages2 and 3.2 Find and prove a mathematical expression for the quantity of interest.For the Tower of Hanoi, this is the recurrence (1.1) that allows us, given the inc lination，to compute T n for any n.3 Find and prove a closed form for our mathematical expression.For the Tower of Hanoi, this is the recurrence solution (1.2).The third stage is the one we will concentrate on throughout this book. In fact, we'll fre quently skip stages I and 2 entirely, because a mathematical expression will be given tous as a starting point. But even then, we'll be getting into subproblems whose solutions will take us through all three stages.Our analysis of the Tower of Hanoi led to the correct answer, but it r equired an“i nductive leap”；we relied on a lucky guess about the answer. One of the main objectives of this book is to explain how a person can solve recurrences without being clairvoyant. For example, we'll see that recurrence (1.1) can be simplified by adding 1 to both sides of the equations：T0+ 1= 1;T n + 1= 2T n-1+ 2, for n >0.Now if we let U n= T n+1，we haveU0 =1；U n= 2U n-1，for n > 0. (1.3)It doesn't take genius to discover that the solution to this recurrence is just U n= 2n；he nce T n= 2n −1. Even a computer could discover this.Concrete MathematicsR. L. Graham, D. E. Knuth, O. Patashnik《Concrete Mathematics》，1.1 ，The Tower Of HanoiR. L. Graham, D. E. Knuth, O. PatashnikSixth printing, Printed in the United States of America1989 by Addison-Wesley Publishing Company，Reference 1-4 pages具体数学R.L.格雷厄姆，D.E.克努特，O.帕塔希尼克《具体数学》，1.1，汉诺塔R.L.格雷厄姆，D.E.克努特，O.帕塔希尼克第一版第六次印刷于美国，韦斯利出版公司，1989年，引用1-4页1 递归问题本章将通过对三个样本问题的分析来探讨递归的思想。
计算机科学与技术毕业设计(论文)外文翻译
本科毕业设计(论文) 外文翻译（附外文原文）系 ( 院 )：信息科学与工程学院课题名称：学生信息管理系统专业(方向)：计算机科学与技术（应用）7.1 Enter ActionMappingsThe Model 2 architecture (see chapter 1) encourages us to use servlets and Java- Server Pages in the same application. Under Model 2, we start by calling a servlet.The servlet handles the business logic and directs control to the appropriate pageto complete the response.The web application deployment descriptor (web.xml) lets us map a URL patternto a servlet. This can be a general pattern, like *.do, or a specific path, like saveRecord.do.Some applications implement Model 2 by mapping a servlet to each business operation. This approach works, but many applications involve dozens or hundredsof business operations. Since servlets are multithreaded, instantiating so manyservlets is not the best use of server resources. Servlets are designed to handle anynumber of parallel requests. There is no performance benefit in simply creatingmore and more servlets.The servlet’s primary job is to interact with the container and HTTP. Handlinga business operation is something that a servlet could delegate to another component. Struts does this by having the ActionServlet delegate the business operationto an object. Using a servlet to receive a request and route it to a handler is knownas the Front Controller pattern [Go3].Of course, simply delegating the business operation to another componentdoes not solve the problem of mapping URIs [W3C, URI] to business operations.Our only way of communicating with a web browser is through HTTP requests and URIs. Arranging for a URI to trigger a business operation is an essential part of developing a web application.Meanwhile, in practice many business operations are handled in similar ways.Since Java is multithreaded, we could get better use of our server resources if wecould use the same Action object to handle similar operations. But for this towork, we might need to pass the object a set of configuration parameters to usewith each operation.So what’s the bottom line? To implement Model 2 in an efficient and flexibleway, we need to:Enter ActionMappings 195♉ Route requests for our business operations to a single servlet♉ Determine which business operation is related to the request♉ Load a multithreaded helper object to handle the business operation♉ Pass the helper object the specifics of each request along with any configuration detail used by this operationThis is where ActionMappings come in.7.1.1 The ActionMapping beanAn ActionMapping (org.apache.struts.action.ActionMapping) describes howthe framework handles each discrete business operation (or action). In Struts,each ActionMapping is associated with a specific URI through its path property. When a request comes in, the ActionServlet uses the path property to select the corresponding ActionMapping. The set of ActionMapping objects is kept in an ActionMappings collection (org.apache.struts.action.ActionMappings). Originally, the ActionMapping object was used to extend the Action objectrather than the Action class. When used with an Action, a mapping gives a specific Action object additional responsibilities and new functionality. So, it was essentiallyan Action decorator [Go4]. Along the way, the ActionMapping evolved into anobject in its own right and can be used with or without an Action.DEFINITION The intent of the decorator pattern is to attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassingfor extending functionality [Go4].The ActionMappings are usually created through the Struts configuration file.For more about this file, see chapter 4.7.1.2 The ActionMappings catalogThe ActionMappings catalog the business logic available to a Struts application.When a request comes in, the servlet finds its entry in the ActionMappings catalogand pulls the corresponding bean.The ActionServlet uses the ActionMapping bean to decide what to do next. Itmay need to forward control off to another resource. Or it may need to populateand validate an ActionForm bean. At some point, it may have to pass control to an Action object, and when the Action returns, it may have to look up an Action-Forward associated with this mapping.196 CHAPTER 7Designing with ActionMappingsThe ActionMapping works like a routing slip for the servlet. Depending onhow the mapping is filled out, the request could go just about anywhere.The ActionMappings represent the core design of a Struts application. If youwant to figure out how a Struts application works, start with the ActionMappings. Ifyou want to figure out how to write a new Struts application, start with the Action- Mappings. The mappings are at the absolute center of every Struts application.In this chapter, we take a close look at the ActionMapping properties andexplore how they help you design the flow of a Struts application.1.0 vs 1.1 In Struts 1.1, ActionMapping subclasses ActionConfig (org.apache. struts.config.ActionConfig) and adds API methods required forbackward compatibility. ActionMapping is not deprecated, and how thehierarchy will be handled in future releases has not been determined.For now, we refer to the ActionMapping class, but you should note thatin Struts 1.1 all of the action properties are actually defined by the ActionConfigsuper class. The ActionMapping class otherwise works thesame way in both versions.7.2 ActionMapping propertiesTable 7.1 describes the base ActionMapping properties. As with other configuration components, developers may extend ActionMapping to provide additionalproperties.Table 7.1 The base ActionMapping propertiesProperty Descriptionpath The URI path from the request used to select this mapping. (API command) forward The context-relative path of the resource that should serve this request via a forward.Exactly one of the forward, include, or type properties must be specified.orinclude The context-relative path of the resource that should serve this request via aninclude. Exactly one of the forward, include, or type properties must be specified.ortype Optionally specifies a subclass oforg.apache.struts.action.ActionMappingthat should be used when instantiating this mapping.className The fully qualified name of the Action class used by this mapping. SinceStruts 1.1ActionMapping properties 197In the sections that follow, we take a look at each of these properties.7.2.1 The path propertyThe ActionMapping URI, or path, will look to the user like just another file onthe web server. But it does not represent a file. It is a virtual reference to our ActionMapping.Because it is exposed to other systems, the path is not really a logical name, likethose we use with ActionForward. The path can include slashes and an extension—as if it referred to a file system—but they are all just part of a single name.The ActionMappings themselves are a “flat” namespace with no type of internalhierarchy whatsoever. They just happen to use the same characters that we areused to seeing in hierarchical file systems.name The name of the form bean, if any, associated with this action. This is not the classname. It is the logical name used in the form bean configuration.roles The list of security roles that may access this mapping.scope The identifier of the scope (request or session) within which the form bean, if any,associated with this mapping will be created.validate Set to true if the validate method of the form bean (if any) associated with thismapping should be called.input Context-relative path of the input form to which control should be returned ifa validationerror is encountered. This can be any URI: HTML, JSP, VM, or another Action- Mapping.parameter General-purpose configuration parameter that can be used to pass extra informationto the Action selected by this ActionMapping.attribute Name of the request-scope or session-scope attribute under which our form bean isaccessed, if it is other than the bean's specified name.prefix Prefix used to match request parameter names to form bean property names, if any.suffix Suffix used to match request parameter names when populating the properties ofour ActionForm bean, if any.unknown Can be set to true if this mapping should be configured as the default for this application(to handle all requests not handled by another mapping). Only one mappingcan be defined as the default unknown mapping within an application.forwards(s) Block of ActionForwards for this mapping to use, if any.exception(s) Block of ExceptionHandlers for this mapping to use, if any.Table 7.1 The base ActionMapping properties (continued)Property DescriptionSinceStruts 1.1SinceStruts 1.1198 CHAPTER 7Designing with ActionMappingsOf course, it can still be useful to treat your ActionMappings as if they werepart of a hierarchy and group related commands under the same "folder." Theonly restriction is that the names must match whatever pattern is used in the application’s deployment description (web.xml) for the ActionServlet. This is usuallyeither /do/* or *.do, but any similar pattern can be used.If you are working in a team environment, different team members can begiven different ActionMapping namespaces to use. Some people may be workingwith the /customer ActionMappings, others may be working with the /vendor ActionMappings. This may also relate to the Java package hierarchy the team isusing. Since the ActionMapping URIs are logical constructs, they can be organizedin any way that suits your project.With Struts 1.1, these types of namespaces can be promoted to applicationmodules. Each team can work independently on its own module, with its own setof configuration files and presentation pages. Configuring your application to use multiple modules is covered in chapter 4.DEFINITION The web runs on URIs, and most URIs map to physical files. If you want to change the resource, you change the corresponding file. Some URIs, likeStruts actions, are virtual references. They do not have a correspondingfile but are handled by a programming component. To change the resource,we change how the component is programmed. But since thepath is a URI and interacts with other systems outside our control, thepath is not a true logical reference—the name of an ActionForward, forinstance. We can change the name of an ActionForward without consultingother systems. It’s an internal, logical reference. If we change thepath to an ActionMapping, we might need to update other systems thatrefer to the ActionMapping through its public URI.7.2.2 The forward propertyWhen the forward property is specified, the servlet will not pass the request to an Action class but will make a call to RequestDispatcher.forward. Since the operationdoes not use an Action class, it can be used to integrate Struts with otherresources and to prototype systems. The forward, include, and type propertiesare mutually exclusive. (See chapter 6 for more information.)7.2.3 The include propertyWhen the include property is specified, the servlet will not pass the request to an Action class but will make a call to RequestDispatcher.include. The operationActionMapping properties 199does not use an Action class and can be used to integrate Struts with other components. The forward, include, and type properties are mutually exclusive. (Seechapter 6 for more information.)7.2.4 The type propertyMost mappings will specify an Action class type rather than a forward or include.An Action class may be used by more than one mapping. The mappings may specifyform beans, parameters, forwards, or exceptions. The forward, include, andtype properties are mutually exclusive.7.2.5 The className propertyWhen specified, className is the fully qualified Java classname of the ActionMapping subclass that should be used for this object. This allows you to use your own ActionMapping subclass with specialized methods and properties. See alsosection 7.4.7.2.6 The name propertyThis property specifies the logical name for the form bean, as given in the formbean segment of the Struts configuration file. By default, this is also the name tobe used when placing the form bean in the request or session context. Use theattribute property of this class to specify a different attribute key.7.2.7 The roles propertyThis property is a comma-delimited list of the security role names that are allowed access to this ActionMapping object. By default, the same system that is used with standard container-based security is applied to the list of roles given here. Thismeans you can use action-based security in lieu of specifying URL patterns in the deployment descriptor, or you can use both together.The security check is handled by the processRoles method of the Request- Processor (org.apache.struts.action.RequestProcessor). By subclassing RequestProcessor, you can also use the roles property with application-based security. See chapter 9 for more about subclassing RequestProcessor.7.2.8 The scope propertyThe ActionForm bean can be stored in the current request or in the session scope (where it will be available to additional requests). While most developers userequest scope for the ActionForm, the framework default is session scope. Tomake request the default, see section 7.4.SinceStruts 1.1SinceStruts 1.1200 CHAPTER 7Designing with ActionMappings7.2.9 The validate propertyAn important step in the lifecycle of an ActionForm is to validate its data before offering it to the business layer. When the validate property for a mapping is true, the ActionServlet will call the ActionForm’s validate method. If validate returns false, the request is forwarded to the resource given by the input property.Often, developers will create a pair of mappings for each data entry form. Onemapping will have validate set to false, so you can create an empty form. Theother has validate set to true and is used to submit the completed form.NOTE Whether or not the ActionForm validate method is called does not relateto the ActionServlet’s validating property. That switch controlshow the Struts configuration file is processed.7.2.10 The input propertyWhen validate is set to true, it is important that a valid path for input be provided. This is where control will pass should the ActionForm validate methodreturn false. Often, this is the address for a presentation page. Sometimes it willbe another Action path (with validate set to false) that is required to generatedata objects needed by the page.NOTE The input path often leads back to the page that submitted the request.While it seems natural for the framework to return the request to whereit originated, this is not a simple task in a web application. A request is oftenpassed from component to component before a response is sent backto the browser. The browser only knows the path it used to retrieve theinput page, which may or may not also be the correct path to use for theinput property. While it may be possible to try and generate a default inputpage based on the HTTP referrer attribute, the Struts designersdeemed that approach unreliable.inputForwardIn Struts 1.0, the ActionMapping input property is always a literal URI. InStruts 1.1, it may optionally be the name of an ActionForward instead. The ActionForward is retrieved and its path property is used as the input property.This can be a global or local ActionForward.To use ActionForwards here instead of literal paths, set the inputForwardattribute on the <controller> element for this module to true:SinceStruts 1.1ActionMapping properties 201<controller inputForward="true">For more about configuring Struts, see chapter 4. For more about ActionForwards,see chapter 6.7.2.11 The parameter propertyThe generic parameter property allows Actions to be configured at runtime. Severalof the standard Struts Actions make use of this property, and the standardScaffold Actions often use it, too. The parameter property may contain a URI, the name of a method, the name of a class, or any other bit of information an Actionmay need at runtime. This flexibility allows some Actions to do double and tripleduty, slashing the number of distinct Action classes an application needs on hand.Within an Action class, the parameter property is retrieved from the mappingpassed to perform:parameter = mapping.getParameter();Multiple parametersWhile multiple parameters are not supported by the standard ActionMappingsclass, there are some easy ways to implement this, including using HttpUtils, a StringTokenizer, or a Properties file (java.util.Properties).HttpUtils. Although deprecated as of the Servlet API 2.3 specification, theHttpUtils package (javax.servlet.http.HttpUtils) provides a static method that parses any string as if it were a query string and returns a Hashtable(java.util.Hashtable):Hashtable parameters = parseQueryString(parameter);The parameter property for your mapping then becomes just another query string, because you might use it elsewhere in the Struts configuration. stringTokenizer. Another simple approach is to delimit the parameters using the token of your choice—such as a comma, colon, or semicolon—and use the StringTokenizer to read them back:StringTokenizer incoming =new StringTokenizer(mapping.getParameter(),";");int i = 0;String[] parameters = new String[incoming.countTokens()]; while (incoming.hasMoreTokens()) {parameters[i++] = incoming.nextToken().trim();}202 CHAPTER 7Designing with ActionMappingsProperties file. While slightly more complicated than the others, another popular approach to providing multiple parameters to an ActionMapping is with a standard Properties files (java.util.Properties). Depending on your needs, the Properties file could be stored in an absolute location in your file system or anywhere on your application’s CLASSPATH.The Commons Scaffold package [ASF, Commons] provides a ResourceUtils package (mons.scaffold.util.ResourceUtils) with methods forloading a Properties file from an absolute location or from your application’s CLASSPATH.7.2.12 The attribute propertyFrom time to time, you may need to store two copies of the same ActionForm inthe same context at the same time. This most often happens when ActionFormsare being stored in the session context as part of a workflow. To keep their names from conflicting, you can use the attribute property to give one ActionForm bean a different name.An alternative approach is to define another ActionForm bean in the configuration, using the same type but under a different name.7.2.13 The prefix and suffix propertiesLike attribute, the prefix and suffix properties can be used to help avoid naming conflicts in your application. When specified, these switches enable aprefix or suffix for the property name, forming an alias when it is populatedfrom the request.If the prefix this was specified, thenthisName=McClanahanbecomes equivalent toname=McClanahanfor the purpose of populating the ActionForm. Either or both parameters would call getName("McClanahan");This does not affect how the properties are written by the tag extensions. It affects how the autopopulation mechanism perceives them in the request.Nested components 2037.2.14 The unknown ActionMappingWhile surfing the Web, most of us have encountered the dreaded 404— page not found message. Most web servers provide some special features for processing requests for unknown pages, so webmasters can steer users in the right direction. Struts offers a similar service for ActionMapping 404s—the unknown ActionMapping. In the Struts configuration file, you can specify one ActionMapping toreceive any requests for an ActionMapping that would not otherwise be matched:<actionname="/debug"forward="/pages/debug.jsp"/>When this option is not set, a request for an ActionMapping that cannot bematched throws400 Invalid path /notHere was requestedNote that by a request for an ActionMapping, we mean a URI that matches the prefix or suffix specified for the servlet (usually /do/* or *.do). Requests for other URI patterns, good or bad, will be handled by other servlets or by the container:/do/notHere (goes to the unknown ActionMapping)/notHere.txt (goes to the container)7.3 Nested componentsThe ActionMapping properties are helpful when it comes to getting an Action torun a business operation. But they tell only part of the story. There is still much todo when the Action returns.An Action may have more than one outcome. We may need to register several ActionForwards so that the Action can take its pick.7.3.1 Local forwardsIn the normal course, an ActionMapping is used to select an Action object to handle the request. The Action returns an ActionForward that indicates which pageshould complete the response.The reason we use ActionForwards is that, in practice, presentation pages areeither often reused or often changed, or both. In either case, it is good practice to encapsulate the page’s location behind a logical name, like “success” or “failure.”The ActionForward object lets us assign a logical name to any given URI.204 CHAPTER 7Designing with ActionMappingsOf course, logical concepts like success or failure are often relative. What represents success to one Action may represent failure to another. Each Action-Mapping can have its own set of local ActionForwards. When the Action asks for a forward (by name), the local set is checked before trying the global forwards. See chapter 6 for more about ActionForwards.Local forwards are usually specified in the Struts configuration file. See chapter4 for details.7.3.2 Local exceptionsMost often, an application’s exception handlers (org.apache.struts.action. ExceptionHandler) can be declared globally. However, if a given ActionMapping needs to handle an exception differently, it can have its own set of local exception handlers that are checked before the global set.Local exceptions are usually specified in the Struts configuration file. Seechapter 4 for details.7.4 Rolling your own ActionMappingWhile ActionMapping provides an impressive array of properties, developers may also provide their own subclass with additional properties or methods. InStruts 1.0, this is configured in the deployment descriptor (web.xml) for the ActionServlet:<init-param><param-name>mapping</param-name><param-value>app.MyActionMapping</param-value></init-param>In Struts 1.1, this is configured in the Struts configuration file as an attribute to the <action-mappings> element:<action-mappings type="app.MyActionMapping">Individual mappings may also be set to use another type through the className attribute:<action className="app.MyActionMapping">For more about configuring Struts, see chapter 4.SinceStruts 1.1Summary 205The framework provides two base ActionMapping classes, shown in table 7.2. They can be selected as the default or used as a base for your own subclasses.The framework default is SessionActionMapping, so scope defaults to session. Subclasses that provide new properties may set them in the Struts configuration using a standard mechanism:<set-property property="myProperty" value="myValue" /> Using this standard mechanism helps developers avoid subclassing the Action- Servlet just to recognize the new properties when it digests the configuration file. This is actually a feature of the Digester that Struts simply inherits.7.5 SummarySun’s Model 2 architecture teaches that servlets and JavaServer Pages should be used together in the same application. The servlets can handle flow control and data acquisition, and the JavaServer Pages can handle the HTML.Struts takes this one step further and delegates much of the flow control anddata acquisition to Action objects. The application then needs only a single servletto act as a traffic cop. All the real work is parceled out to the Actions and theStruts configuration objects.Like servlets, Actions are efficient, multithreaded singletons. A single Actionobject can be handling any number of requests at the same time, optimizing your server’s resources.To get the most use out of your Actions, the ActionMapping object is used as a decorator for the Action object. It gives the Action a URI, or several URIs, and away to pass different configuration settings to an Action depending on which URIis called.In this chapter, we took a close look at the ActionMapping properties andexplained each property’s role in the scheme of things. We also looked at extendingthe standard ActionMapping object with custom properties—just in case yourscheme needs even more things.Table 7.2 The default ActionMapping classesActionMapping Descriptionorg.apache.struts.action.SessionActionMapping Defaults the scope property to sessionorg.apache.struts.action.RequestActionMapping Defaults the scope property to request206 CHAPTER 7Designing with ActionMappingsIn chapter 8, the real fun begins. The configuration objects covered so far aremainly a support system. They help the controller match an incoming requestwith a server-side operation. Now that we have the supporting players, let’s meet the Struts diva: the Action object.7.1 进入ActionMappingModel 2 架构(第1章)鼓励在同一个应用中使用servlet和JSP页面。
计算机专业毕业设计论文外文文献中英文翻译——java对象
1 . Introduction To Objects1.1The progress of abstractionAll programming languages provide abstractions. It can be argued that the complexity of the problems you’re able to solve is directly related to the kind and quality of abstraction。
By “kind” I mean，“What is it that you are abstracting?” Assembly language is a small abstraction of the underlying machine. Many so—called “imperative” languages that followed （such as FORTRAN，BASIC, and C) were abstractions of assembly language。
These languages are big improvements over assembly language，but their primary abstraction still requires you to think in terms of the structure of the computer rather than the structure of the problem you are trying to solve。
The programmer must establish the association between the machine model (in the “solution space，” which is the place where you’re modeling that problem, such as a computer) and the model of the problem that is actually being solved (in the “problem space,” which is the place where the problem exists). The effort required to perform this mapping, and the fact that it is extrinsic to the programming language，produces programs that are difficult to write and expensive to maintain，and as a side effect created the entire “programming methods” industry.The alter native to modeling the machine is to model the problem you’re trying to solve。
计算机专业毕业设计论文外文文献中英文翻译(Object)
外文资料Object landscapes and lifetimesTechnically, OOP is just about abstract data typing, inheritance, and polymorphism, but other issues can be at least as important. The remainder of this section will cover these issues.One of the most important factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object controlled? There are different philosophies at work here. C++ takes the approach that control of efficiency is the most important issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocation and release, and control of these can be very valuable in some situations. However, you sacrifice flexibility because you must know the exact quantity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided design, warehouse management, or air-traffic control, this is too restrictive.The second approach is to create objects dynamically in a pool of memory called the heap. In this approach, you don't know until run-time how many objects you need, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is running. If you need a new object, you simply make it on the heap at the point that you need it. Because the storage is managed dynamically, at run-time, the amount of time required to allocate storage on the heap is significantly longer than the time to create storage on the stack. (Creating storage on the stack is often a single assembly instruction tomove the stack pointer down, and another to move it back up.) The dynamic approach makes the generally logical assumption that objects tend to be complicated, so the extra overhead of finding storage and releasing that storage will not have an important impact on the creation of an object. In addition, the greater flexibility is essential to solve the general programming problem.Java uses the second approach, exclusively]. Every time you want to create an object, you use the new keyword to build a dynamic instance of that object.There's another issue, however, and that's the lifetime of an object. With languages that allow objects to be created on the stack, the compiler determines how long the object lasts and can automatically destroy it. However, if you create it on the heap the compiler has no knowledge of its lifetime. In a language like C++, you must determine programmatically when to destroy the object, which can lead to memory leaks if you don’t do it correctly (and this is a common problem in C++ programs). Java provides a feature called a garbage collector that automatically discovers when an object is no longer in use and destroys it. A garbage collector is much more convenient because it reduces the number of issues that you must track and the code you must write. More important, the garbage collector provides a much higher level of insurance against the insidious problem of memory leaks (which has brought many a C++ project to its knees).The rest of this section looks at additional factors concerning object lifetimes and landscapes.1 Collections and iteratorsIf you don’t know how many objects you’re going to need to solve a particular problem, or how long they will last, you also don’t know how to store those objects. How can you know how much space to create for thoseobjects? You can’t, since that information isn’t known until run-time.The solution to most problems in object-oriented design seems flippant: you create another type of object. The new type of object that solves this particular problem holds references to other objects. Of course, you can do the same thing with an array, which is available in most languages. But there’s more. This new object, generally called a container(also called a collection, but the Java library uses that term in a different sense so this book will use “container”), will expand itself whenever necessary to accommodate everything you place inside it. So you don’t need to know how manyobjects you’re going to hold in a container. Just create a container object and let it take care of the details.Fortunately, a good OOP language comes with a set of containers as part of the package. In C++, it’s part of the Standard C++ Library and is sometimes called the Standard Template Library (STL). Object Pascal has containers in its Visual Component Library (VCL). Smalltalk has a very complete set of containers. Java also has containers in its standard library. In some libraries, a generic container is considered good enough for all needs, and in others (Java, for example) the library has different types of containers for different needs: a vector (called an ArrayListin Java) for consistent access to all elements, and a linked list for consistent insertion at all elements, for example, so you can choose the particular type that fits your needs. Container libraries may also include sets, queues, hash tables, trees, stacks, etc.All containers have some way to put things in and get things out; there are usually functions to add elements to a container, and others to fetch those elements back out. But fetching elements can be more problematic, because a single-selection function is restrictive. What if you want to manipulate or compare a set of elements in the container instead of just one?The solution is an iterator, which is an object whose job is to select the elements within a container and present them to the user of the iterator. As a class, it also provides a level of abstraction. This abstraction can be used to separate the details of the container from the code that’s accessing that container. The container, via the iterator, is abstracted to be simply a sequence. The iterator allows you to traverse that sequence without worrying about the underlying structure—that is, whether it’s an ArrayList, a LinkedList, a Stack, or something else. This gives you the flexibility to easily change the underlying data structure without disturbing the code in your program. Java began (in version 1.0 and 1.1) with a standard iterator, called Enumeration, for all of its container classes. Java 2 has added a much more complete container library that contains an iterator called Iterator that does more than the older Enumeration.From a design standpoint, all you really want is a sequence that can be manipulated to solve your problem. If a single type of sequence satisfied all of your needs, there’d be no reason to have different kinds. There are two reasons that you need a choice of containers. First, containers provide different types of interfaces and external behavior.A stack has a different interface and behavior than that of a queue, which is different from that of a set or a list. One of these might provide a more flexible solution to your problem than the other. Second, different containers have different efficiencies for certain operations. The best example is an ArrayList and a LinkedList. Both are simple sequences that can have identical interfaces and external behaviors. But certain operations can have radically different costs. Randomly accessing elements in an ArrayList is a constant-time operation; it takes the same amount of time regardless of the element you select. However, in a LinkedList it is expensive to move through the list to randomly selectan element, and it takes longer to find an element that is further down the list. On the other hand, if you want to insert an element in the middle of a sequence, it’s much cheaper in a LinkedList than in an ArrayList. These and other operations have different efficiencies depending on the underlying structure of the sequence. In the design phase, you might start with a LinkedList and, when tuning for performance, change to an ArrayList. Because of the abstraction via iterators, you can change from one to the other with minimal impact on your code.In the end, remember that a container is only a storage cabinet to put objects in. If that cabinet solves all of your needs, it doesn’t really matter how it is implemented (a basic concept with most types of objects). If you’re working in a programming environment that has built-in overhead due to other factors, then the cost difference between an ArrayList and a LinkedList might not matter. You might need only one type of sequence. You can even imagine the “perfect”container abstraction, which can automatically change its underlying implementation according to the way it is used.2 The singly rooted hierarchyOne of the issues in OOP that has become especially prominent since the introduction of C++ is whether all classes should ultimately be inherited from a single base class. In Java (as with virtually all other OOP languages) the answer is “yes”and the name of this ultimate base class is simply Object. It turns out that the benefits of the singly rooted hierarchy are many.All objects in a singly rooted hierarchy have an interface in common, so they are all ultimately the same type. The alternative (provided by C++) is that you don’t know that everything is the same fundamental type. From a backward-compatibility standpoint this fits the model of C better and can be thought of as less restrictive, but when you want to do full-onobject-oriented programming you must then build your own hierarchy to provide the same convenience that’s built into other OOP languages. And in any new class library you acquire, some other incompatible interface will be used. It requires effort (and possibly multiple inheritance) to work the new interface into your design. Is the extra “flexibility” of C++ worth it? If you need it—if you have a large investment in C—it’s quite valuable. If you’re starting from scratch, other alternatives such as Java can often be more productive.All objects in a singly rooted hierarchy (such as Java provides) can be guaranteed to have certain functionality. You know you can perform certain basic operations on every object in your system. A singly rooted hierarchy, along with creating all objects on the heap, greatly simplifies argument passing (one of the more complex topics in C++).A singly rooted hierarchy makes it much easier to implement a garbage collector (which is conveniently built into Java). The necessary support can be installed in the base class, and the garbage collector can thus send the appropriate messages to every object in the system. Without a singly rooted hierarchy and a system to manipulate an object via a reference, it is difficult to implement a garbage collector.Since run-time type information is guaranteed to be in all objects, you’ll never end up with an object whose type you cannot determine. This is especially important with system level operations, such as exception handling, and to allow greater flexibility in programming.3 Collection libraries and support for easy collection useBecause a container is a tool that you’ll use frequently, it makes sense to have a library of containers that are built in a reusable fashion, so you can take one off the shelf Because a container is a tool that you’ll use frequently, it makes sense to have a library of containers that are built in a reusable fashion, so you can take one off the shelf and plugit into your program. Java provides such a library, which should satisfy most needs.Downcasting vs. templates/genericsTo make these containers reusable, they hold the one universal type in Java that was previously mentioned: Object. The singly rooted hierarchy means that everything is an Object, so a container that holds Objects can hold anything. This makes containers easy to reuse.To use such a container, you simply add object references to it, and later ask for them back. But, since the container holds only Objects, when you add your object reference into the container it is upcast to Object, thus losing its identity. When you fetch it back, you get an Object reference, and not a reference to the type that you put in. So how do you turn it back into something that has the useful interface of the object that you put into the container?Here, the cast is used again, but this time you’re not casting up the inheritance hierarchy to a more general type, you cast down the hierarchy to a more specific type. This manner of casting is called downcasting. With upcasting, you know, for example, that a Circle is a type of Shape so it’s safe to upcast, but you don’t know that an Object is necessarily a Circle or a Shape so it’s hardly safe to downcast unless you know that’s what you’re dealing with.It’s not completely dangerous, however, because if you downcast to the wrong thing you’ll get a run-time error called an exception, which will be described shortly. When you fetch object references from a container, though, you must have some way to remember exactly what they are so you can perform a proper downcast.Downcasting and the run-time checks require extra time for the runningprogram, and extra effort from the programmer. Wouldn’t it make sense to somehow create the container so that it knows the types that it holds, eliminating the need for the downcast and a possible mistake? The solution is parameterized types, which are classes that the compiler can automatically customize to work with particular types. For example, with a parameterized container, the compiler could customize that container so that it would accept only Shapes and fetch only Shapes.Parameterized types are an important part of C++, partly because C++ has no singly rooted hierarchy. In C++, the keyword that implements parameterized types is “template.” Java currently has no parameterized types since it is possible for it to get by—however awkwardly—using the singly rooted hierarchy. However, a current proposal for parameterized types uses a syntax that is strikingly similar to C++ templates.译文对象的创建和存在时间从技术角度说，OOP（面向对象程序设计）只是涉及抽象的数据类型、继承以及多形性，但另一些问题也可能显得非常重要。
英文文献及翻译(计算机专业)
英文文献及翻译(计算机专业)The increasing complexity of design resources in a net-based collaborative XXX common systems。
design resources can be organized in n with design activities。
A task is formed by a set of activities and resources linked by logical ns。
XXX managementof all design resources and activities via a Task Management System (TMS)。
which is designed to break down tasks and assign resources to task nodes。
This XXX。
2 Task Management System (TMS)TMS is a system designed to manage the tasks and resources involved in a design project。
It poses tasks into smaller subtasks。
XXX management of all design resources and activities。
TMS assigns resources to task nodes。
XXX。
3 Collaborative DesignCollaborative design is a process that XXX a common goal。
In a net-based collaborative design environment。
n XXX n for all design resources and activities。
计算机专业毕业设计--英文文献(含译文)
外文文献原文THE TECHNIQUE DEVELOPMENT HISTORY OF JSPThe Java Server Pages( JSP) is a kind of according to web of the script plait distance technique, similar carries the script language of Java in the server of the Netscape company of server- side JavaScript( SSJS) and the Active Server Pages(ASP) of the Microsoft. JSP compares the SSJS and ASP to have better can expand sex, and it is no more exclusive than any factory or some one particular server of Web. Though the norm of JSP is to be draw up by the Sun company of, any factory can carry out the JSP on own system.The After Sun release the JSP( the Java Server Pages) formally, the this kind of new Web application development technique very quickly caused the people's concern. JSP provided a special development environment for the Web application that establishes the high dynamic state. According to the Sun parlance, the JSP can adapt to include the Apache WebServer, IIS4.0 on the market at inside of 85% server product.This chapter will introduce the related knowledge of JSP and Databases, and JavaBean related contents, is all certainly rougher introduction among them basic contents, say perhaps to is a Guide only, if the reader needs the more detailed information, pleasing the book of consult the homologous JSP.1.1 GENERALIZEThe JSP(Java Server Pages) is from the company of Sun Microsystems initiate, the many companies the participate to the build up the together of the a kind the of dynamic the state web the page technique standard, the it have the it in the construction the of the dynamic state the web page the strong but the do not the especially of the function. JSP and the technique of ASP of the Microsoft is very alike. Both all provide the ability that mixes with a certain procedure code and is explain by the language engine to carry out the procedure code in the code of HTML. Underneath we are simple of carry on the introduction to it.JSP pages are translated into servlets. So, fundamentally, any task JSP pages can perform could also be accomplished by servlets. However, this underlying equivalence does not mean that servlets and JSP pages are equally appropriate in all scenarios. The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other. After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language. But it still matters which you choose.JSP provides the following benefits over servlets alone:• It is easier to write and maintain the HTML. Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.• You can use standard Web-site development tools. Even HTML tools that know nothing about JSP can be used because they simply ignore the JSP tags.• You can divide up your development team. The Java programmers can work on the dynamic code. The Web developers can concentrate on the presentation layer. On large projects, this division is very important. Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSP instead. By no means. Almost all projects will use both. For some requests in your project, you will use servlets. For others, you will use JSP. For still others, you will combine them with the MVC architecture . You want the appropriate tool for the job, and servlets, by themselves, do not complete your toolkit.1.2 SOURCE OF JSPThe technique of JSP of the company of Sun, making the page of Web develop the personnel can use the HTML perhaps marking of XML to design to turn the end page with format. Use the perhaps small script future life of marking of JSP becomes the dynamic state on the page contents.( the contents changes according to the claim of)The Java Servlet is a technical foundation of JSP, and the large Web applies the development of the procedure to need the Java Servlet to match with with the JSP and then can complete, this name of Servlet comes from the Applet, the local translation method of now is a lot of, this book in order not to misconstruction, decide the direct adoption Servlet but don't do any translation, if reader would like to, can call it as" small service procedure". The Servlet is similar to traditional CGI, ISAPI, NSAPI etc. Web procedure development the function of the tool in fact, at use the Java Servlet hereafter, the customer need not use again the lowly method of CGI of efficiency, also need not use only the ability come to born page of Web of dynamic state in the method of API that a certain fixed Web server terrace circulate. Many servers of Web all support the Servlet, even not support the Servlet server of Web directly and can also pass the additional applied server and the mold pieces to support the Servlet. Receive benefit in the characteristic of the Java cross-platform, the Servlet is also a terrace irrelevant, actually, as long as match the norm of Java Servlet, the Servlet is complete to have nothing to do with terrace and is to have nothing to do with server of Web. Because the Java Servlet is internal to provide the service by the line distance, need not start a progress to the each claimses, and make use of the multi-threadingmechanism can at the same time for several claim service, therefore the efficiency of Java Servlet is very high.But the Java Servlet also is not to has no weakness, similar to traditional CGI, ISAPI, the NSAPI method, the Java Servlet is to make use of to output the HTML language sentence to carry out the dynamic state web page of, if develop the whole website with the Java Servlet, the integration process of the dynamic state part and the static state page is an evil-foreboding dream simply. For solving this kind of weakness of the Java Servlet, the SUN released the JSP.A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual "embrace and extend" strategy. At this point, Gosling lightheartedly interjected "You mean disgrace and distend."Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here. The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags. For example, Cold Fusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact, JSP not only adopted the general idea, it even used many of the same special tags as ASP did.The JSP is an establishment at the model of Java servlets on of the expression layer technique, it makes the plait write the HTML to become more simple.Be like the SSJS, it also allows you carry the static state HTML contents and servers the script mix to put together the born dynamic state exportation. JSP the script language that the Java is the tacit approval, however, be like the ASP and can use other languages( such as JavaScript and VBScript), the norm of JSP also allows to use other languages.1.3 JSP CHARACTERISTICSIs a service according to the script language in some one language of the statures system this kind of discuss, the JSP should be see make is a kind of script language.However, be a kind of script language, the JSP seemed to be too strong again, almost can use all Javas in the JSP.Be a kind of according to text originally of, take manifestation as the central development technique, the JSP provided all advantages of the Java Servlet, and, when combine with a JavaBeans together, providing a kind of make contents and manifestation that simple way that logic separate. Separate the contents and advantage of logical manifestations is, the personnel who renews the page external appearance need not know the code of Java, and renew the JavaBeans personnel also need not be design the web page of expert in hand, can use to take the page of JavaBeans JSP to define the template of Web, to build up a from have the alike external appearance of the website that page constitute. JavaBeans completes the data to provide, having no code of Java in the template thus, this means that these templates can be written the personnel by a HTML plait to support. Certainly, can also make use of the Java Servlet to control the logic of the website, adjust through the Java Servlet to use the way of the document of JSP to separate website of logic and contents.Generally speaking, in actual engine of JSP, the page of JSP is the edit and translate type while carry out, not explain the type of. Explain the dynamic state web page development tool of the type, such as ASP, PHP3 etc., because speed etc. reason, have already can't satisfy current the large electronic commerce needs appliedly, traditional development techniques are all at to edit and translate the executive way change, such as the ASP → ASP+;PHP3 → PHP4.In the JSP norm book, did not request the procedure in the JSP code part( be called the Scriptlet) and must write with the Java definitely. Actually, have some engines of JSP are adoptive other script languages such as the EMAC- Script, etc., but actually this a few script languages also are to set up on the Java, edit and translate for the Servlet to carry out of. Write according to the norm of JSP, have no Scriptlet of relation with Java also is can of, however, mainly lie in the ability and JavaBeans, the Enterprise JavaBeanses because of the JSP strong function to work together, so even is the Scriptlet part not to use the Java, edit and translate of performance code also should is related with Java.1.4 JSP MECHANISMTo comprehend the JSP how unite the technical advantage that above various speak of, come to carry out various result easily, the customer must understand the differentiation of" the module develops for the web page of the center" and" the page develops for the web page of the center" first.The SSJS and ASP are all in several year ago to release, the network of that time is still very young, no one knows to still have in addition to making all business, datas and the expression logic enter the original web page entirely heap what better solvethe method. This kind of model that take page as the center studies and gets the very fast development easily. However, along with change of time, the people know that this kind of method is unwell in set up large, the Web that can upgrade applies the procedure. The expression logic write in the script environment was lock in the page, only passing to shear to slice and glue to stick then can drive heavy use. Express the logic to usually mix together with business and the data logics, when this makes be the procedure member to try to change an external appearance that applies the procedure but do not want to break with its llied business logic, apply the procedure of maintenance be like to walk the similar difficulty on the eggshell. In fact in the business enterprise, heavy use the application of the module already through very mature, no one would like to rewrite those logics for their applied procedure.HTML and sketch the designer handed over to the implement work of their design the Web plait the one who write, make they have to double work-Usually is the handicraft plait to write, because have no fit tool and can carry the script and the HTML contents knot to the server to put together. Chien but speech, apply the complexity of the procedure along with the Web to promote continuously, the development method that take page as the center limits sex to become to get up obviously.At the same time, the people always at look for the better method of build up the Web application procedure, the module spreads in customer's machine/ server the realm. JavaBeans and ActiveX were published the company to expand to apply the procedure developer for Java and Windows to use to come to develop the complicated procedure quickly by" the fast application procedure development"( RAD) tool. These techniques make the expert in the some realm be able to write the module for the perpendicular application plait in the skill area, but the developer can go fetch the usage directly but need not control the expertise of this realm.Be a kind of take module as the central development terrace, the JSP appeared. It with the JavaBeans and Enterprise JavaBeans( EJB) module includes the model of the business and the data logic for foundation, provide a great deal of label and a script terraces to use to come to show in the HTML page from the contents of JavaBeans creation or send a present in return. Because of the property that regards the module as the center of the JSP, it can drive Java and not the developer of Java uses equally. Not the developer of Java can pass the JSP label( Tags) to use the JavaBeans that the deluxe developer of Java establish. The developer of Java not only can establish and use the JavaBeans, but also can use the language of Java to come to control more accurately in the JSP page according to the expression logic of the first floor JavaBeans.See now how JSP is handle claim of HTTP. In basic claim model, a claimdirectly was send to JSP page in. The code of JSP controls to carry on hour of the logic processing and module of JavaBeanses' hand over with each other, and the manifestation result in dynamic state bornly, mixing with the HTML page of the static state HTML code. The Beans can be JavaBeans or module of EJBs. Moreover, the more complicated claim model can see make from is request other JSP pages of the page call sign or Java Servlets.The engine of JSP wants to chase the code of Java that the label of JSP, code of Java in the JSP page even all converts into the big piece together with the static state HTML contents actually. These codes piece was organized the Java Servlet that customer can not see to go to by the engine of JSP, then the Servlet edits and translate them automatically byte code of Java.Thus, the visitant that is the website requests a JSP page, under the condition of it is not knowing, an already born, the Servlet actual full general that prepared to edit and translate completes all works, very concealment but again and efficiently. The Servlet is to edit and translate of, so the code of JSP in the web page does not need when the every time requests that page is explain. The engine of JSP need to be edit and translate after Servlet the code end is modify only once, then this Servlet that editted and translate can be carry out. The in view of the fact JSP engine auto is born to edit and translate the Servlet also, need not procedure member begins to edit and translate the code, so the JSP can bring vivid sex that function and fast developments need that you are efficiently.Compared with the traditional CGI, the JSP has the equal advantage. First, on the speed, the traditional procedure of CGI needs to use the standard importation of the system to output the equipments to carry out the dynamic state web page born, but the JSP is direct is mutually the connection with server. And say for the CGI, each interview needs to add to add a progress to handle, the progress build up and destroy by burning constantly and will be a not small burden for calculator of be the server of Web. The next in order, the JSP is specialized to develop but design for the Web of, its purpose is for building up according to the Web applied procedure, included the norm and the tool of a the whole set. Use the technique of JSP can combine a lot of JSP pages to become a Web application procedure very expediently.JSP six built-in objectsrequest for:The object of the package of information submitted by users, by calling the object corresponding way to access the information package, namely the use of the target users can access the information.response object:The customer's request dynamic response to the client sent the data.session object1. What is the session: session object is a built-in objects JSP, it in the first JSP pages loaded automatically create, complete the conversation of management.From a customer to open a browser and connect to the server, to close the browser, leaving the end of this server, known as a conversation.When a customer visits a server, the server may be a few pages link between repeatedly, repeatedly refresh a page, the server should bethrough some kind of way to know this is the same client, which requires session object.2. session object ID: When a customer's first visit to a server on the JSP pages, JSP engines produce a session object, and assigned aString type of ID number, JSP engine at the same time, the ID number sent to the client, stored in Cookie, this session objects, and customers on the establishment of a one-to-one relationship. When a customer to connect to the server of the other pages, customers no longer allocated to the new session object, until, close your browser, the client-server object to cancel the session, and the conversation, and customer relationship disappeared. When a customer re-open the browser to connect to the server, the server for the customer to create a new session object.aplication target1. What is the application:Servers have launched after the application object, when a customer to visit the site between the various pages here, this application objects are the same, until the server is down. But with the session difference is that all customers of the application objects are the same, that is, all customers share this built-in application objects.2. application objects commonly used methods:(1) public void setAttribute (String key, Object obj): Object specified parameters will be the object obj added to the application object, and to add the subject of the designation of a keyword index.(2) public Object getAttribute (String key): access to application objects containing keywords for.out targetsout as a target output flow, used to client output data. out targets for the output data.Cookie1. What is Cookie:Cookie is stored in Web server on the user's hard drive section of the text. Cookie allow a Web site on the user's computer to store information on and then get back to it.For example, a Web site may be generated for each visitor a unique ID, and then to Cookie in the form of documents stored in each user's machine.If you use IE browser to visit Web, you will see all stored on your hard drive on the Cookie. They are most often stored in places: c: \ windows \ cookies (in Window2000 is in the C: \ Documents and Settings \ your user name \ Cookies).Cookie is "keyword key = value value" to preserve the format of the record.2. Targets the creation of a Cookie, Cookie object called the constructor can create a Cookie. Cookie object constructor has two string .parameters: Cookie Cookie name and value.Cookie c = new Cookie ( "username", "john");3. If the JSP in the package good Cookie object to send to the client, the use of the response addCookie () method.Format: response.addCookie (c)4. Save to read the client's Cookie, the use of the object request getCookies () method will be implemented in all client came to an array of Cookie objects in the form of order, to meet the need to remove the Cookie object, it is necessary to compare an array cycle Each target keywords.JSP的技术发展历史Java Server Pages(JSP)是一种基于web的脚本编程技术，类似于网景公司的服务器端Java脚本语言—— server-side JavaScript(SSJS)和微软的Active Server Pages(ASP)。
计算机毕业设计中英文文献
At present, there are many b/s, c/s structure examination systems based on-line, this paper first introduced most of these systems’ formed and developed process, and structures. Then, analysis these systems, and pointed out that there still have many defects about them, just like the update and the service to these systems .Thinking based on these produces, and now the J2EE technical is becoming mature, we thinking about is this technical can be used in examination systems, so we mentioned a on-line system based on J2EE structure. Compared to other systems, and also analysis its’ advantages, we introduced this structure’s construction and technical as emphasize. Finally, makeJ2EE technical a expectation and it can progress quiet great and have a nice foreground. With the educational thinking and scientific and technological progress update to the traditional pen and paper as the main tool for examinations revealed many shortcomings increasingly prominent.1.became the main object of interest in taking the examination candidates can not be activated. Has always been the traditional way of examination papers to students the teacher made test, when test, test what, how to judge the whole by the teacher decided to test scores, students have been in a passive position and even forced.2.Therefore, the main test became teachers, students, have become the subject of the real object. Thus, the exam, students passive defense, a passive response or even fraud. Examination of the torture process is the process of serving the students, no fun at all, let alone in the examination process glorious life in flash.3.Important results than process, candidates can not objectively reflect the real level of ability. Traditional examinations only one goal: results of the examinations. Both teachers and students value this, the general view is that the higher levels of test scores high and low test scores were low. But in fact the examination process for various reasons, an examination candidate fails to play at this level of a normal or failed to fully play a level, such examination can not objectively reflect the candidate's level.With the rapid development of network technology, many foreign universities and other sectors of society have been set up distance education, remote education through computer networks and training. Now, computer hardware technology has reached a very high level. However, distance learning software development is still in its infancy, with the further development of this technology continues to require better, more comprehensive software system which is applied to distance education to go, which gives software designers made more High design requirements.Distance education includes many areas, such as teaching systems, answering system and examination system and so on. One very important aspect is the examination system, it is also the most difficult to achieve the link. In China, although distance education has been vigorously developed, but the current school examinations with the community's most traditional examinations, in this way,After the organization of a test at least five steps, namely artificial out of question, candidates test, artificial grading, performance evaluation and analysis papers. Clearly, as the type of examination and examination requirements of increasing the continuous improvement will be increasing the workload of teachers and their work will be a very cumbersome and very error-prone things can be said that the traditional test method hasbeen Can not meet the exam requirements. With the rapid development of computer applications, web applications continue to expand, such as distance education and the emergence of virtual universities, etc., and these applications are gradually deep into millions of households.Admittedly, online teaching has a very broad application prospects, assistant teaching building of the network path is absolutely inevitable. It is worth mentioning that the distance education in China after years of development in the post has become increasingly mature. Over the years, China has been very seriously the development of distance education, distance education in the university education system, now or at the initiation stage. Facts have proved that today's society, no matter what the industry is engaged in the future, online exams are irreplaceable status, its applications are among the most widely used of all the disciplines, the establishment of online examination system is the premise of such a background generated.Over the years, along with the development of the school, either from hardware or from software on my school have certain basic conditions, the University building of online examination system is imperative. Produced by our "online examination system"is mainly for the majority of students and their teachers to provide a convenient place, so that we can learn more about the Internet in different places all aspects of the operating system, and teacher exchanges, exchange views with other students, and Online test and so on. The majority of students believe that it will provide convenient and efficient way of learning.The results of the project to provide a database of online test site, the students through the campus network or the Internet to access the site, students can follow the recommendations of teachers or their own plans for what they have learned self-test; teachers can provide the environment through the web site for students Dynamic management of the learning and test scores based on site records of each student is given an objective evaluation. Online examination system to reduce the workload of teachers and improve work efficiency, while also improving the quality of the examination, so that the notary exam tends to be more objective and more to stimulate students interest in learning.The database is online examination system mainly uses JSP, Java, HTML, SQL database technologies and tools, and integration of today's popular web application development and integration tools for Java development environment, MyEclipse DreamWeaver overall design follows the software engineering methods, through needs analysis, general design , the preparation of documentation and code, module testing and system implementation stages. Here are several techniques and methods to make this an overview.Database to provide online examination system for the candidates to sign up, online testing and other functions. Is based on the computer network applications. It can make the test without time, place restrictions on the one hand, greatly reducing the teacher a question, change the volume of work, on the other hand to enable students to test their learning at any time, so that learning efficiency is greatly improved. Online examination system in the generation of questions, the submission of papers, marking and other results can be done automatically on the network, as long as the formation of a maturereal paperless exam to exam.This phase of the system through initial research and target analysis, and to demonstrate the feasibility of the program. We are here mainly from the technical feasibility, economic feasibility and operational feasibility were analyzed.Software development cycle is generally 2-3 months, developing the necessary hardware and software facilities are currently able to take the majority of PC computer system, the development cost is not high. Currently, most units have high-performance computer and LAN, the software system installation, deployment, operation and maintenance units will not increase the cost too high.Development of the relevant information required by the system through the existing system of investigation related to acquisition, other necessary software applications, hardware systems are easy to obtain. Therefore, the development costs low. The introduction of using this system, compared with the traditional way, with high efficiency, low cost, high-quality features, you can save a lot of manpower, material and financial resources. So, from an economic point of view, the system is feasible.Browser-based online exam, the key technology is the dynamic Web page display and management, from database to obtain the appropriate papers in the data, and collect user input data to control the examination process. Jsp and SQL using the latest technology development, management interface used in all client and candidate B / S Mode, system deployment, application, maintenance more convenient. At the same time, SqlServer database provides database management capabilities, the technical solution is mature and feasible.Technical feasibility to consider whether the existing technology the successful completion of development work, development of hardware and software configured to meet the demand. This site is JSP development language, debugging a relatively simple, the current computer hardware configuration is also fully able to meet the needs of development, so technically it is absolutely feasible. Software: due to the currentstand-alone model is relatively mature, so mature and viable software development platform, they speed, large capacity, high reliability, low price, can meet the system requirements.Feasibility of running the organization structure, existing staff and institutions and environmental adaptability of the system and personnel training additional feasibility. Current information technology is already quite popular, various operators have very high levels, so the run is feasible.The development of this system is a typical Mis development, mainly for data processing, including data collection, data transformation, and data output of the various report forms. Using the popular JSP + SQLSERVER 2000 system, with no technical problems.From the time point of view, in two months to learn the knowledge and the development of the hotel management system, time is a bit tight, but not impossible, to function through more than two months basically.①All technical data are as lawful.②the development process there is no intellectual property rights.③not copying any hotel management system, there is no infringement of copyright.④the development process not involved in any legal responsibility.In summary, this system development is technically, economically, legally are completely reliable.To implement a software system needs analysis should be conducted first, so can the design of software to meet user's various functions. Here the design of the online examination system needs analysis.Database online examination system should have the following requirements:(1) The test corresponds to a particular object, so the system needs through effective authentication before they can login. And the system needed to manage the session functions. In the examination process for tracking test status.(2) and system access is generally divided into two kinds: administrators and students. Different identities with different privileges and functions.(3) the administrator of the questions and candidates need effective management, responsible for questions of entry and updates and modifications of the classification of questions, each time before the exam, candidates need to state examination center exam environment and initialization. Note that, given the test environment is generally room, close the distance between the examination, in order to do online test specifications for each candidate, the amount of questions and examination papers should be the same, but the questions Not the same.System has to be a good paper and recycling upload function to ensure the accuracy of information transfer. System has to be a friendly interface to ensure smooth progress of the examination candidates. Because the papers need teachers mark the subjective questions, it may take some time to check the results. However, if the paper is composed by objective kinds of questions, candidates can check the end of the exam to their score. System provides statistics on test scores and query management functions. System should have a good safety management.The current examination system, there are still many is based on the c / s mode, each time accompanied by a system upgrade, should update the software on each client,time-consuming and labor-intensive. Fortunately, as technology evolves, based on the b / s mode of online examination system more and more, and gradually occupy a dominant position. It overcomes the c / s mode, many of the shortcomings of the traditional-based C / S mode changes to the examination system based on B / S mode test system that enables users on any computer, as long as access to the Internet to connect Use the service, greatly simplifying the operation, to provide users with convenient. The other hand, the management and marking for teachers to provide a convenient and improved efficiency. But according to my multi-party observation and research, found that most of the online examination system models are developed based on the page, each page contains all the features you need to use the logic, lead to code repetition rate, the structure is not clear, Maintenance upgrades is also very time-consuming and manpower. Given this situation, so we added the concept of J2EE to online examination system to make the system more easy to upgrade and maintain.目前国内基于B/S、C/S结构的数据库在线考试系统产品已经有许多，本文首先介绍了这些考试系统的形成和发展过程，大致结构。
计算机专业中英文翻译外文翻译文献翻译
英文参考文献及翻译Linux - Operating system of cybertimes Though for a lot of people , regard Linux as the main operating system to make up huge work station group, finish special effects of " Titanic " make , already can be regarded as and show talent fully. But for Linux, this only numerous news one of. Recently, the manufacturers concerned have announced that support the news of Linux to increase day by day, users' enthusiasm to Linux runs high unprecedentedly too. Then, Linux only have operating system not free more than on earth on 7 year this piece what glamour, get the favors of such numerous important software and hardware manufacturers as the masses of users and Orac le , Informix , HP , Sybase , Corel , Intel , Netscape , Dell ,etc. , OK?1.The background of Linux and characteristicLinux is a kind of " free (Free ) software ": What is called free,mean users can obtain the procedure and source code freely , and can use them freely , including revise or copy etc.. It is a result of cybertimes, numerous technical staff finish its research and development together through Inte rnet, countless user is it test and except fault , can add user expansion function that oneself make conveniently to participate in. As the most outstanding one in free software, Linux has characteristic of the following:(1)Totally follow POSLX standard, expand the network operatingsystem of supporting all AT&T and BSD Unix characteristic. Because of inheritting Unix outstanding design philosophy , and there are clean , stalwart , high-efficient and steady kernels, their all key codes are finished by Li nus Torvalds and other outstanding programmers, without any Unix code of AT&T or Berkeley, so Linu x is not Unix, but Linux and Unix are totally compatible.(2)Real many tasks, multi-user's system, the built-in networksupports, can be with such seamless links as NetWare , Windows NT , OS/2 ,Unix ,etc.. Network in various kinds of Unix it tests to be fastest in comparing and assess efficiency. Support such many kinds of files systems as FAT16 , FAT32 , NTFS , Ex t2FS , ISO9600 ,etc. at the same time .(3) Can operate it in many kinds of hardwares platform , including such processors as Alpha , SunSparc , PowerPC , MIPS ,etc., to various kinds of new-type peripheral hardwares, can from distribute on global numerous programmer there getting support rapidly too.(4) To that the hardware requires lower, can obtain very good performance on more low-grade machine , what deserves particular mention is Linux outstanding stability , permitted " year " count often its running times.2.Main application of Linux At present,Now, the application of Linux mainly includes:(1) Internet/Intranet: This is one that Linux was used most at present, it can offer and include Web server , all such Inter net services as Ftp server , Gopher server , SMTP/POP3 mail server , Proxy/Cache server , DNS server ,etc.. Linux kernel supports IPalias , PPP and IPtunneling, these functions can be used for setting up fictitious host computer , fictitious service , VPN (fictitious special-purpose network ) ,etc.. Operating Apache Web server on Linux mainly, the occupation rate of market in 1998 is 49%, far exceeds the sum of such several big companies as Microsoft , Netscape ,etc..(2) Because Linux has outstanding networking ability , it can be usedin calculating distributedly large-scaly, for instance cartoon making , scientific caculation , database and file server ,etc..(3) As realization that is can under low platform fullness of Unix that operate , apply at all levels teaching and research work of universities and colleges extensively, if Mexico government announce middle and primary schools in the whole country dispose Linux and offer Internet service for student already.(4) Tabletop and handling official business appliedly. Application number of people of in this respect at present not so good as Windows of Microsoft far also, reason its lie in Lin ux quantity , desk-top of application software not so good as Windows application far not merely, because the characteristic of the freedom software makes it not almost have advertisement thatsupport (though the function of Star Office is not second to MS Office at the same time, but there are actually few people knowing).3.Can Linux become a kind of major operating system?In the face of the pressure of coming from users that is strengthened day by day, more and more commercial companies transplant its application to Linux platform, comparatively important incident was as follows, in 1998 ①Compaq and HP determine to put forward user of requirement truss up Linux at their servers , IBM and Dell promise to offer customized Linux system to user too. ②Lotus announce, Notes the next edition include one special-purpose edition in Linux. ③Corel Company transplants its famous WordPerfect to on Linux, and free issue. Corel also plans to move the other figure pattern process products to Linux platform completely.④Main database producer: Sybase , Informix , Oracle , CA , IBM have already been transplanted one's own database products to on Linux, or has finished Beta edition, among them Oracle and Informix also offer technical support to their products.4.The gratifying one is, some farsighted domestic corporations have begun to try hard to change this kind of current situation already. Stone Co. not long ago is it invest a huge sum of money to claim , regard Linux as platform develop a Internet/Intranet solution, regard this as the core and launch Stone's system integration business , plan to set up nationwide Linux technical support organization at the same time , take the lead to promote the freedom software application and development in China. In addition domestic computer Company , person who win of China , devoted to Linux relevant software and hardware application of system popularize too. Is it to intensification that Linux know , will have more and more enterprises accede to the ranks that Linux will be used with domestic every enterprise to believe, more software will be planted in Linux platform. Meanwhile, the domestic university should regard Linux as the original version and upgrade already existing Unix content of courses , start with analysing the source code and revising the kernel and train a large number of senior Linux talents, improve our country's own operating system. Having only really grasped the operating system, the software industry of our country could be got rid of and aped sedulously at present, the passive state led by the nose by others, create conditions for revitalizing the software industry of our country fundamentally.中文翻译Linux—网络时代的操作系统虽然对许多人来说，以Linux作为主要的操作系统组成庞大的工作站群，完成了《泰坦尼克号》的特技制作，已经算是出尽了风头。
计算机专业外文文献论文翻译
本科毕业设计外文文献及译文文献、资料题目：Evolving Java Without Changingthe Language文献、资料来源：/articles/evolving-java-no-lang-change 文献、资料发表（出版）日期：院（部）：专业：班级：姓名：学号：指导教师：翻译日期：外文文献：Evolving Java Without Changing the Language In "The Feel of Java" James Gosling stated that: Java is a blue collar language. It's not PhD thesis material but a language for a job. Java feels very familiar to many different programmers because I had a very strong tendency to prefer things that had been used a lot over things that just sounded like a good idea.The extraordinary success of Java offers weight to the notion that this was a sensible approach, and if it remains an important goal for Java today, then it makes sense that the language should continue to evolve relatively slowly. In addition to this, the fact that Java is a mature, widely used language causes its evolution to be fraught with difficulty. For one thing, each feature added to the language can change the way it feels in subtle and often unpredictable ways, risking alienating developers who have already adopted it as their language of choice. For another, a feature that makes perfect sense on its own may interact with other features of the language in awkward or unexpected ways. Worse, once a language feature has been added it is all but impossible to remove even if it turns out to be detrimental to the language as a whole. To justify adding a new feature, a language designer must be highly confident that it will be of long term benefit to the language rather than a short term or fashionable solution to a problem that rapidly becomes redundant. To mitigate the risk a language designer will typically experiment by creating a separate language or branch, such as the Pizza language used to experiment with Java's generics, prior to their implementation. The problem with this approach is that the audience for such experiments is both small and self-selecting; obviously they will all be interested in language features, and many may be academics or researchers. An idea which plays well to such an audience may still play badly when it is incorporated into the main language and general programmers start to work with it.To get a sense of this, consider the closures debate that became so heated for Java 7. Implementations for the main proposals (and some others) have been available for some time but no consensus has emerged. In consequence Sun decided that JDK 7 will not get full closures support. The core argument came down to whether Java had become as complex as it could afford to be when generics (and in particular the wildcard syntax) were added to Java 5; andwhether the addition of full support for closures was justified when Java already has a more limited form through anonymous inner classes. Two important use cases for adding full closures support were to simplify working with the fork/join API that is being added to JDK 7 to improve multi-core programming, and to help with resource clean-up. Josh Bloch's ARM block proposal, which is now expected to be in JDK 7 via Project Coin, offers an alternative solution to the latter problem. Dr. Cliff Click's research on a scalable, non-blocking programming style for Java offers an alternative approach to fork/join that may be more appropriate as the number of processor cores increases. If this were to happen, then the uses for closures in Java may arguably be too limited to justify their inclusion.It remains important though that a programming language continues to develop at some level. This article therefore examines three alternative techniques for adding new language features to Java that don't require changes to the language itself - using a custom Domain Specific Language, exploiting the Java 6 annotation processor to add optional language features via a library, and moving the syntactic sugar from the language to the IDE. Each offers the potential to allow a wide audience of mainstream developers to experiment with the new features over the medium term in a non-invasive manner, and the best ideas can then filter down for inclusion in the core language.Custom DSLsThe most widely discussed of the three is the Domain-Specific Language or DSL. There is some disagreement on exactly what the term means, but for the purposes of this discussion we'll refer to it simply as a language that has been created with a narrow focus to solve a particular problem, rather than as a general purpose language designed to solve every computing problem. As such we would expect a DSL to be non-Turing complete and for the most part this is the case. There are edge cases of course. Postscript, for example, is a Turing complete language but also qualifies as a DSL using our definition.As the above example also illustrates, the idea of a DSL is not new. Other familiar DSLs include Regular Expressions, XSLT, Ant, and JSP, all of which require some sort of custom parser to process them. Martin Fowler also suggests that fluent interfaces/APIs can be considered a second type of DSL, which he refers to as an internal DSL. His definition is that an internal DSL is developed directly within the host language. This was a common practice amongst bothLisp and Smalltalk programmers, and more recently the Ruby community has been popularising the technique.Whilst many well-known DSLs are commercially developed and maintained, some enterprise development teams have used the technique to create a language that allows them to rapidly explore aspects of their problem domain. It isn't however as common as it might be, perhaps because DSLs have a fairly intimidating barrier to entry. The team has to design the language, build the parser and possibly other tools to support the programming team, and train each new developer that joins the team on how the DSL works. Here the emergence of tools to specifically support DSL development could significantly change the landscape. Intentional Software's Intentional Domain Workbench, which has been in development longer than Java has been around, is the first significant implementation of such a tool. The project started life at Microsoft Research, and Dr. Charles Simonyi's 1995 paper "The Death of Computer Languages, the Birth of Intentional Programming" describes his vision. In 2002 Simonyi founded Intentional Software to continue working on his ideas and a hugely impressive video demo of the system is available. The product itself is at 1.0 status, but access is restricted to very limited partners.Other software houses are also exploring the concepts, amongst them JetBrains, well respected for their IntelliJ IDEA Java IDE, who have recently released the 1.0 version of their Meta Programming System (MPS). MPS doesn't use a parser, instead working with the Abstract Syntax Tree (AST) directly. It provides a text-like projectional editor which allows the programmer to manipulate the AST, and is used to write languages and programs. For each node in the tree a textual projection is created - as the programmer works with the projection, the change is reflected in the node. This approach allows you to extend and embed languages in any combination (often referred to as language composing) promoting language re-use. JetBrains are using the product internally and have recently released YouTrack, a bug tracking product developed using the system.The Java 6 Annotation ProcessorWhilst DSLs are less common in more mainstream languages such as Java than they are in Ruby, Smalltalk and Lisp, recent developments in the Java language, in particular the annotation processor which was added in Java 6, offer new possibilities for developers looking to use them in Java. The JPA 2.0 criteria API that will ship as part of Java EE 6, itself a DSL, offers anexample. Here the annotation processor builds up a metamodel type for each persistent class in the application. Whilst it would be perfectly possible for the developer to hand craft the metamodel in Java, it would be both tedious and error prone. The use of the annotation processor eliminates that pain and, since the annotation processor is built into Java 6, the approach requires no specific IDE support – an IDE delegates to the annotation processor triggered by the compiler, and the metadata model is generated on the fly.Using the annotation processor it is also possible for a library to add a new language feature. Bruce Chapman's prototype "no closures" proposal, for example, uses the technique to provide a mechanism for casting a method to a Single Abstract Method (SAM) type which compiles on top of Java 6. During our conversation Chapman pointed out that the SAM type also supports free variables, a key aspect of a closure:The method body can declare additional parameters beyond those required for the Single **********************************************.Theseparameterscanhavevaluesbound to them at the point where you obtain an instance of the SAM type, and are then passed to the method each time it is invoked.Chapman also set up the Rapt project to explore other uses of the technique, and has added implementations for two language changes - Multiline Strings and XML literals - that were considered for JDK 7 but won't now make it into the final release. Java could even get a form of closures support using this approach. When asked about this, Chapman said: We are just finishing a Swing project which we used it for. We have found a couple of minor bugs around generic types, one recently discovered remains to be fixed but other than that it seems quite nice to use, and nobody has been wanting to rush back to use conventional anonymous inner classes.Project Lombok, another project exploring the the annotation processor, pushes the technique still further. In effect Lombok uses annotation processing as a hook to run a Java agent that re-writes various javac internals based on the annotations. Since it is manipulating internal classes it is probably not suited to production use (internal classes can change even between minor releases of the JVM) but the project is an eye-opening example of just what can be done using the annotation processor, including:•Support for properties using a pair of @Getter and/or @Setter annotations with varying access levels, e.g. @Setter(AccessLevel.PROTECTED) private String name;•The @EqualsAndHashCode annotation, which generates hashCode() and equals() implementations from the fields of your object•The @ToString annotation, which generates an implementation of the toString() method •The @data method, which is equivalent to combining @ToString, @EqualsAndHashCode, @Getter on all fields, and @Setter on all non-final fields along with a constructor to initialize your final fieldsOther language experimentation, such as removing checked exceptions from Java, can also be done using this approach.Whilst the annotation processor technique opens up a welcome new route to language experimentation, care needs to be taken that the generated code can be easily read by developers, not just by the machine. Chapman made a number of suggestions during our conversation:Generate source code not bytecode, and pay attention to formatting (indenting especially) in the generated code. The compiler won't care whether it is all on one line or not, but your users will. I even sometimes add comments and javadoc in the source code generated by my annotation processors where appropriate.Hopefully if the technique becomes more prevalent IDEs will also make it easier to view the code that is to be generated at compile time.Syntactic Sugar in the IDEBruce Chapman also touches on our third technique - moving the syntactic sugar from the language to the IDE - in his blog and he elaborated on his ideas during our conversation. It is already routine for Java IDEs to create portions of boilerplate code for you such as the getters and setters of a class, but IDE developers are beginning to push the concept further. JetBrains' IntelliJ 9 offers a terse code block syntax for inner classes similar to a closure, which a developer can also type. Acting like code folds, these can then be expanded into the full anonymous inner classes which the compiler works with - this allows developers who prefer to stick with the standard anonymous inner class syntax to do so. A similar plug-in for Eclipse also exists. The key point here is that the "alternate" syntax is just a view of the actual code which the compiler and any source management tools continue to work with. Thus the developer should be able to switchviews between either form (like expanding or collapsing a code fold), and anyone without access to the definition of the sugar just sees the normal Java code. Chapman writes:There are many details to work out in order to make this easily accessible, but long term I see developers relatively easily defining a two way sugaring/desugaring transformation (jackpot is a good start for how this might be done), trying them out, evolving them and sharing the good ones with colleagues and the community. The advantages of this are almost the same as for a language change, without the disadvantages. The very best could become ubiquitous and then form the basis of an actual language change if necessary to get rid of any remaining "noise" not possible with this approach.Since syntactic sugar has to map to another (more verbose) language feature it cannot offer complete closure support; there are some features of BGGA closures for example that cannot be mapped to anonymous inner classes, and so they couldn't be implemented through this approach. Nevertheless the idea opens up the possibility of having various new syntaxes for representing anonymous inner classes, similar to BGGA syntax or FCM syntax, and allowing developers to pick the syntax they want to work with. Other language features, such as the null-safe Elvis operator, could certainly be done this way. To experiment further with the idea this NetBeans module also developed by Chapman, is what he describes as a "barely functional" prototype for Properties using this approach.ConclusionIn language development there is always a trade-off between stability and progress. The advantage that all of these techniques bring is that they don't affect the platform or the language. In consequence they are more tolerant to mistakes and are therefore more conducive to rapid and radical experimentation. With developers freely able to experiment we should begin to see more people separately tackling the poor signal to noise ratio of some common boilerplate such as the anonymous inner class syntax, mixing and evolving these ideas to some optimum form that adds the most value in the most cases. It will be fascinating to see how developers use these different approaches to push the Java platform in new directions.中文译文：不改变语言的前提下推进Java演进James Gosling在“The Feel of Java”中说过：Java是一种蓝领语言，它并不是博士的论文材料而是可以完成工作上的语言。
英文文献及翻译（计算机专业）
英文文献及翻译（计算机专业）NET-BASED TASK MANAGEMENT SYSTEMHector Garcia-Molina, Jeffrey D. Ullman, Jennifer WisdomABSTRACTIn net-based collaborative design environment, design resources become more and more varied and complex. Besides com mon in formatio n man ageme nt systems, desig n resources can be orga ni zed in connection with desig n activities.A set of activities and resources linked by logic relations can form a task. A task has at least one objective and can be broken down into smaller ones. So a design project can be separated in to many subtasks formi ng a hierarchical structure.Task Management System (TMS) is designed to break down these tasks and assig n certa in resources to its task no des. As a result of decompositi on. al1 desig n resources and activities could be man aged via this system.KEY WORDS : Collaborative Design, Task Management System (TMS), Task Decompositi on, In formati on Man ageme nt System1 IntroductionAlong with the rapid upgrade of request for adva need desig n methods, more and more desig n tool appeared to support new desig n methods and forms. Desig n in a web en vir onment with multi-part ners being invo Ived requires a more powerful and efficie nt man ageme ntsystem .Desig n part ners can be located everywhere over the n et with their own organizations. They could be mutually independent experts or teams of tens of employees. This article discussesa task man ageme nt system (TMS) which man agesdesig n activities and resources by break ing dow n desig n objectives and re-orga nizing desig n resources in conn ecti on with the activities. Compari ng with com mon information management systems (IMS) like product data management system and docume nt man ageme nt system, TMS can man age the whole desig n process. It has two tiers which make it much more flexible in structure.The lower tier con sists of traditi onal com mon IMSS and the upper one fulfillslogic activity management through controlling a tree-like structure, allocating design resources andmaking decisions about how to carry out a design project. Its functioning paradigm varies in differe nt projects depending on the project ' s scale and purpose. As a result of this structure, TMS can separate its data model from its logic mode1.lt could bring about structure optimization and efficiency improvement, especially in a large scale project.2 Task Management in Net-Based Collaborative Design Environment 2.1 Evolution of the Design Environment During a net-based collaborative design process, designers transform their working environment from a single PC desktop to LAN, and even extend to WAN. Each desig n part ner can be a sin gle expert or a comb in ati on of many teams of several subjects, even if they are far away from each other geographically. In the net-based collaborative desig n environment, people from every term inal of the net can excha nge their information interactively with each other and send data to authorized roles via their desig n tools. The Co Desig n Space is such an environment which provides a set of these tools to help desig n part ners com muni cate and obta in desig n in formatio n. Codesign Space aims at improving the efficiency of collaborative work, making en terprises in crease its sen sitivity to markets and optimize the con figurati on of resource.2.2 Management of Resources and Activities in Net-Based Collaborative EnvironmentThe expansion of design environment also caused a new problem of how to organize the resources and design activities in that environment. As the number of desig n part ners in creases, resources also in crease in direct proporti on. But relatio ns betwee n resources in crease in square ratio. To orga nize these resources and their relations needs an integrated management system which can recognize them and provide to desig ners in case of they are n eeded.One soluti on is to use special in formatio n man ageme nt system (IMS).A n IMS can provide database,file systems and in/out in terfaces to man age a give n resource. For example there are several IMS tools in Co Design Space such as Product Data Man ageme nt System, Docume nt Man ageme nt System and so on. These systemsca n provide its special information which design users want.But the structure of design activities is much more complicated than these IM S could man age, because eve n a simple desig n project may invo Ive differe nt desig n resources such asdocuments, drafts and equipments. Not only product data or documents, design activities also need the support of organizations in design processes. This article puts forward a new design system which attempts to integrate different resources into the related desig n activities. That is task man ageme nt system (TMS).3 Task Breakdown Model3.1 Basis of Task BreakdownWhen people set out to accomplish a project, they usually separate it into a seque nee of tasks and finish them one by one. Each desig n project can be regarded as an aggregate of activities, roles and data. Here we define a task as a set of activities and resources and also having at least one objective. Because large tasks can be separated into small ones, if we separate a project target into several lower—level objectives, we defi ne that the project is broke n dow n into subtasks and each objective maps to a subtask. Obviously if each subtask is accomplished, the project is surely finished. So TMS integrates design activities and resources through planning these tasks.Net-based collaborative design mostly aims at products development. Project man agers (PM) assig n subtasks to desig ners or desig n teams who may locate in other cities. The designers and teams execute their own tasks under the constraints which are defined by the PM and negotiated with each other via the collaborative design en vir onment. So the desig ners and teams are in depe ndent collaborative part ners and have in compact coupli ng relati on ships. They are drive n together only by theft desig n tasks. After the PM have finished decomposing the project, each designer or team leader who has bee n assig ned with a subtask become a low-class PM of his own task. And he can do the same thing as his PM done to him, re-breaking down and re-assig ning tasks.So we put forward two rules for Task Breakdown in a net-based environment, in compact coupli ng and object-drive n. In compact coupli ng mea ns the less relati on ship betwee n two tasks. Whe n two subtasks were coupled too tightly, therequireme nt for com muni cati on betwee n their desig ners will in crease a lot. Too much com muni cati on wil1 not only waste time and reduce efficiency, but also bring errors. It will become much more difficult to man age project process tha n usually in this situati on. On the other hand every task has its own objective. From the view point of PM of a superior task each subtask could be a black box and how to execute these subtasks is unknown. The PM concerns only the results and constraints of these subtasks, and may never concern what will happe n in side it.3.2 Task Breakdown MethodAccord ing to the above basis, a project can be separated into several subtasks. And whe n this separati ng con ti nu es, it will fin ally be decomposed into a task tree. Except the root of the tree is a project, all eaves and branches are subtasks. Since a design project can be separatedinto a task tree, all its resources can be added to it depe nding on their relati on ship. For example, a Small-Sized-Satellite.Desig n (3SD) project can be broke n dow n into two desig n objectives as Satellite Hardware. Design (SHD) and Satellite-Software-Exploit (SSE). And it also has two teams. Desig n team A and desig n team B which we regard as desig n resources. Whe n A is assig ned to SSE and B to SHD. We break dow n the project as show n in Fig 1.It is alike to man age other resources in a project in this way. So whe n we defi ne a collaborative design project ' s task m od e lshould first claim the project ' s targets These targets in clude fun cti onal goals, performa nee goals, and quality goals and so on. Then we could confirm how to execute this project. Next we can go on to break dow n it. The project can be separated into two or more subtasks since there are at least two part ners in acollaborative project. Either we could separate the project into stepwise tasks, which have time seque nee relati on ships in case of some more complex projects and the n break dow n the stepwise tasks accord ing to their phase-to-phase goals.There is also another trouble in executing a task breakdown. When a task is broke n into several subtasks; it is not merely “ a simple sum motioof other tasks. In most cases their subtasks could have more complex relati ons.To solve this problem we use constraints. There are time sequenee constraint (TSC) and logic constraint (LC). The time sequence constraint defines the time relati on ships among subtasks. The TSC has four differe nt types, FF, FS, SF and SS. F means finish and S presents start. If we say Tabb is FS and lag four days, it means Tb should start no later tha n four days after Ta is fini shed.The logic constraint is much more complicated. It defines logic relationship among multiple tasks.Here is give n an example:Task TA is separated into three subtasks, Ta, T b and Tc. But there are two more rules.Tb and Tc can not be executed until T a is finished.Tb and T c can not be executed both that means if Tb was executed, Tc should not be executed, and vice versa. This depe nds on the result of Ta.So we say Tb and Tc have a logic con stra int. After finishing break ing dow n the tasks, we can get a task tree as Fig, 2 illustrates.4 TMS Realization4.1 TMS StructureAccord ing to our discussi on about task tree model and taskbreakdow n basis, we can develop a Task Man ageme nt System (TMS) based on Co Desig n Space using Java Ian guage, JSP tech no logy and Microsoft SQL 2000. The task man ageme nt system ' s structure is shown in Fig. 3.TMS has four main modules namely Task Breakdown, Role Management, Statistics and Query and Data In tegrati on. The Task Breakdow n module helps users to work out task tree. Role Management module performs authentication and authorization of access control. Statistics and Query module is an extra tool for users to find more information about their task. The last Data Integration Module provides in/out in terface for TMS with its peripheral en vir onment.4.2 Key Points in System Realization4.2.1 Integration with Co Design SpaceCo Desig n Space is an in tegrated in formatio n man ageme nt system which stores, shares and processes desig n data and provides a series of tools to support users. These tools can share all information in the database because they have a universal DataModel. Which is defined in an XML (extensible Markup Language) file, and has a hierarchical structure. Based on this XML structure the TMS h data mode1 definition is orga ni zed as follow ing.Notes: Element “Pros” a task node object, and “Processis a task set object which contains subtask objects and is bel ongs to a higher class task object. One task object can have no more than one “ Presseso b jects. According to this definition,“ Prcs o bjects are organized in a tree-formation process. The other objects are resources, such as task link object ( “ Presage ”sk notes ( “ ProNotes ”, )and task documents( “Attachments ” ) .These resources are shared in Co Design d atabase文章出处：计算机智能研究[J],47 卷，2007: 647-703基于网络的任务管理系统摘要在网络与设计协同化的环境下，设计资源变得越来越多样化和复杂化。
计算机专业外文文献翻译
毕业设计（论文）外文文献翻译（本科学生用）题目：Plc based control system for the music fountain 学生姓名：_ ___学号：060108011117 学部（系）: 信息学部专业年级: _06自动化（1）班_指导教师： ___职称或学位：助教__20 年月日外文文献翻译（译成中文1000字左右）：【主要阅读文献不少于5篇，译文后附注文献信息，包括：作者、书名（或论文题目）、出版社（或刊物名称）、出版时间（或刊号）、页码。
提供所译外文资料附件（印刷类含封面、封底、目录、翻译部分的复印件等，网站类的请附网址及原文】英文节选原文：Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. Unspoken rule is that you’ll find mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of PLC controllers, program execution, memory operation, overseeing input and setting up of an output. PLC controllers have complex routines for memory checkup in order to ensure that PLC memory was not damaged (memory checkup is done for safety reasons).Generally speaking, CPU unit makes a great number of check-ups of the PLC controller itself so eventual errors would be discovered early. You can simply look at any PLC controller and see that there are several indicators in the form. of light diodes for error signalization.System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this operating system it also contains a user program translated forma ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development.User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status. The real status of an input is stored either as “1”or as “0”in a specific memory bit/ each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in used program. For example, time value, or counter value would be stored in this part of the memory.PLC controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). This practically means that each PLC controller can programmed through a computer if you have the software needed for programming. Today’s transmission computers are ideal for reprogramming a PLC controller in factory itself. This is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to time whether program in a PLC has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in PLC controllers to ensure execution only of good programs). Almost every program for programming a PLC controller possesses various useful options such as: forced switching on and off of the system input/outputs (I/O lines),program follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented ladder diagram allows any technician to understand thoroughly how system functions.Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you’ll find electrical supply as a separate module. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current. This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC.中文翻译：从结构上分，PLC分为固定式和组合式（模块式）两种。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
The After Sun release the JSP( the Java Server Pages) formally, the this kind of new Web application development techniue very uickly caused the people's concern. JSP provided a special development environment for the Web application that establishes the high dynamic state. According to the Sun parlance, the JSP can adapt to include the Apache WebServer, IIS4.0 on the market at inside of 85% server product.
f according to web of the script plait distance techniue, similar carries the script language of Java in the server of the Netscape company of server- side JavaScript( SSJS) and the Active Server Pages(ASP) of the Microsoft. JSP compares the SSJS and ASP to have better can expand sex, and it is no more exclusive than any factory or some one particular server of Web. Though the norm of JSP is to be draw up by the Sun company of, any factory can carry out the JSP on own system.
This chapter will introduce the related knowledge of JSP and Databases, and JavaBean related contents, is all certainly rougher introduction among them basic contents, say perhaps to is a Guide only, if the reader needs the more detailed information, pleasing the book of consult the homologous JSP.
1.1 GENERALver Pages) is from the company of Sun Microsystems initiate, the many companies the participate to the build up the together of the a kind the of dynamic the state web the page techniue standard, the it have the it in the construction the of the dynamic state the web page the strong but the do not the especially of the function. JSP and the techniue of ASP of the Microsoft is very alike. Both all provide the ability that mixes with a certain procedure code and is explain by the language engine to carry out the procedure code in the code of HTML. Underneath we are simple of carry on the introduction to it.
JSP pages are translated into servlets. So, fundamentally, any task JSP pages can perform could also be accomplished by servlets. However, this underlying euivalence does not mean that servlets and JSP pages are eually appropriate in all scenarios. The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other. After all, anything you can do on a particular computer platform in the Java programming