毕业设计外文资料翻译_文献英文原文

毕业设计外文资料
题目面对对象技术
学院信息科学与工程学院
专业计算机科学与技术
班级计软1202
学生刘桂斌
学号20121214073
指导教师史桂娴，王海燕
二〇一六年三月二十日
Object Technology2004, Vol.14 (2), pp.20.
Object Technology
Timothy A.Budd
Abstract Object technology is a new approach to developing software that allows programmers to create objects, a combination of data and program instructions. This new technology has been steadily developed since the late 1960s and promises to be one of the major ingredients in the response to the ongoing software crisis.
Keywords Object technology Optimization
1.1 Introduction to OT
There exists a critical technology that is changing the way we conceive, build, use and evolve our computer systems. It is a technology that many companies are adopting to increase their efficiency, reduce costs and adapt to a dynamic marketplace. It is called Object Technology (OT).
By allowing the integration of disparate and non compatible source, OT has the potential to precipitate a revolution in information systems design on a par with that caused in computer hardware by the introduction of the computer chip. Yet OT is not a new
phenomenon. Development and product releases have been ongoing since its origin many years ago. However, the recent emphasis task of enterprise information technology integration has brought OT into the spotlight.
OT promises to provide component-level software objects that can be quickly combined to build new applications that respond to changing business conditions. Once used, objects may be reused in other applications, lowering development costs and speeding up the development process. Because objects communicate by sending messages that can be understood by other objects, large integrated systems are easier to assemble.
Each object is responsible for a specific function within either an application or a distributed system. That means that as the business changes, individual object may be easily upgraded, augmented or replaced, leaving the rest of the system untouched. This directly reduces the cost of maintenance and the timing and extendibility of new systems.
1.2 OT-based Products
The current market for OT-based products can be divided into four major segments: ·Languages and programming tools
·Developers’ toolkits
·Object-Oriented database
·Object-Oriented CASE tools
The largest segment of the current market for OT-based products is languages and
programming tools. Products in this area include language compliers for C++, Smalltalk, Common Lisp Object System (CLOS), Eiffel, Ada and Objective-C, as well as extensions to PASCAL and Modula-2.
Products in this category are available from a variety of vendors. Increasingly, the trend in this group is to offer the language compliers with associated development tools as part of a complete development environment.
Developers’ toolkits account for the next largest part of the OT market. These products are designed to develop a program that enables a developer to easily do one of two things. The first is interfacing an application to distributed environment. The second is developing a graphical screen through a product.
By providing developers with higher level description language and reusable
components, products in this category give developers an easy and cost effective way to begin producing object-oriented systems.
An important component in this category is the relatively new area of end-users tools. This element is important because organizing and analying the increasingly large amounts of data that computer systems are capable of collecting is a key problem.
Object-oriented database management systems are one of the most interesting and rapidly growing segments of the OT market. A number of companies, including systems vendors like Digital and HP, and start-ups such as Object Design, Servio, and Objectivity, have all produced products.
These products, dubbed ‖Objectbases‖, fill an important need by storing complex
objects as a single entity. The objectbase products allow objects to be stored, retrieved and shared in much the same way as data is stored in a relational database management system. The value of an objectbase, as opposed to a database, is best described as following: ―Object databases offer a better way to store objects because they provide all of the traditional database services without the overhead of disassembling and reassembling
objects every time they are stored and retrieved. Compared with an object database, storing complex objects in a relational database is tedious at best. It’s like having to disassembling your car each night rather than just putting it into the gar age!‖
Over the next few years, a shift from proprietary CASE implementations to those based on the object paradigm can be expected. This area has lagged growth from earlier projections. OT-based CASE tools will have to emerge as a viable product category to address the wide scale development of large systems. This category also include those tools that are methodological in nature.
1.3 0bject-oriented Programming
Object-oriented programming (OOP) is a new approach to developing software that allows programmers to create objects, a combination of data and program instructions. Traditional programming methods keep data, such as files, independent of the programs that work with the data. Each traditional program, t5herfore, must define how the data will be used for that particular program. This often results in redundant programming code that must be changed every time the structure of the data is changed, such as when a new field is added to a file. With OOP, the program instructions and data are combined into objects that can be used repeatedly by programmers whenever they need them. Specific
instructions, called methods define how the object acts when it is used by a program.
With OOP, programmers define classes of objects. Each class contains the methods that are unique to that class. Each class can have one or more subclasses. Each subclass contains the methods of its higher level classes plus whatever methods are unique to the subclass. The OOP capability to pass methods to lower levels is called ―inheritance‖.
A specific instance of an object contains all methods from its higher level classes plus any methods that a unique to the object. When an OOP object is sent an instruction to do something, called a message, unlike a traditional program, the message does not have to tell the OOP object exactly what to do. What to do is defined by the methods that the OOP object contains or has inherited.
Object—oriented programming can bring many advantages to users. It can bring productivity gains as high as 1000 to 1500 percent instead of the 10 or 15 percent gains
available from structured programming methods. It allows large complex systems to be built which are not economically feasible using traditional programming techniques. It allows program modifications to be made more easily. It could mean two different user interfaces within an application, one for the user who likes to type, and another for the users who just want to shout at the terminal.
Objects can be viewed as reusable components, and once the programmer has developed a library of these components, he can minimize the amount of new coding required. One user envisions a commercial library of objects which could be purchased by
programmers and reused for various applications. But creating a library is no simple task because the integrity of the original software design is critical. Reusability can be a mixed blessing for users, too, as a programmers has to be able to find the object he needs. But if productivity is your aim, reusability is worth the risks.
The long-term productivity of systems is enhanced by object-oriented programming. Because of the modular nature of the code, programs are more malleable. This is particularly beneficial for applications that will be used for many years, during which company needs may change and make software modifications necessary.
Software reliability can be improved by object-oriented programming. Since the objects are repeatedly tested in a variety of applications, bugs are more likely to be found and corrected. Object-oriented programming also has potential benefits in parallel processing. Execution speed under object oriented methods will improve with parallel processing.
1.4 Object-oriented DBMS
A shift toward object-oriented DBMSs does not have to replace relational DNMS. As its name implies, it is orientation rather than a full-blown DBMS model. As such, it can blend with and build on the relational schema.
Object-oriented DBMSs integrate a variety of real-world data types –such as business procedures and policies, graphics, pictures, voice, and an non-tated text. Current relational products are not equipped to handle them efficiently. Data types in RDBMSs are more commonly record-oriented and expressed in numbers and text.
Object orientation also makes contributions to application development efficiency.
makes the data function, attributes, and relationships an integral part of the object. In this way, objects can be reused and replicated. You can query the data on its functions, attributes, and relationships.
By contrast, most RDBMSs demand that the knowledge associated with the data be written into and maintained separately in each application program.
Object orientation is going to be available in two forms: one for those who need and want a radical change, and one for those who want some of its advantages without going through a major conversion.
The first form of object-oriented DBMS focused largely on the computer-aided design (CAD) market, which needed to store complex data types such as the graphics involved with an aircraft design.
The second form is made up of the leading RDBMS vendors who support the concept of integrating object management capabilities whit their current line of relational products. Sybase, Inc, the first vendor to introduce an object-oriented capability,
offers Sybase , which enables the user to program a limited number of business procedures along with the data types in a server’s database engine . Any client attempting a transaction that does not conform to these procedures is simply rejected by the database. That capability enables users to shorten the development cycle, since integrity logic and business rules no longer need to be programmed into each application.
This approach reduces maintenance costs as well, since any changes in the procedure can be made once at the server level instead of several times within all the affected applications.
Last, the server-level procedures increase the system’s performance, since the operations are taking place closer to where the data is actually stored.。