lesson 18 The Systems Development Life Cycle

Sentence Explanations
Before taking a look at each of the steps in the SDLC, it is important to realize that these six steps do not always follow one another in a strict sequence. For example, analysis and design are frequently interwoven.
接下来，调研工作检查待解决问题的特性，解决该问 题的工作范围，可能的解决方案以及每种建议方案的 近似费用和效益。
Sentence Explanations
The main output of the preliminary investigation is the feasibility report, which includes the systems analyst's findings on the status of the existing system, and the benefits and fearsibility of changing to a new system.
当提出建设一个新系统或改造现有系统的建议时，第 一个步骤是初步调研或可行性研究。调研的目的是较 快地定义和评估问题域，判断是否值得进一步研究并 对可能采取地措施提出建议。
Sentence Explanations
Accordingly, the investigation examines such issues as the nature of the problem, the scope of the work involved to solve it, possible solutions, and the approximate costs and benefits of each proposed solution.
数据收集的目的是收集在研系统运行任务的信息。数 据收集过程试图确定用户为了更好执行任务所需的资 源。然后，数据收集工作应该提出一些可能的解决方 案。
Sentence Explanations
Data flow diagrams show the relationships between activities that are part of a system as well as the data or information flowing into and out of each activity.
初步调研的主要输出是可行性研究报告，它包括系统 分析师对现存系统状态的评价，改变系统的效益和可 行性。
Sentence Explanations
Feasibility is commonly measured using a few different perspectives, such as whether the organization has, or can acquire, the hardware, software, and personnel needed to implement the new system; whether the new system would fit well with the other systems in the organization; whether the estimated benefits of the new system outweigh the estimated costs; and so forth.
Lesson Eighteen
The Systems Development Life Cycle
系统开发生命周期
vocabulary
systems development life cycle system acquisition feasibility study systems analyst feasibility report System analysis data flow diagrams decision table decision tree system flowcharts data dictionary 系统开发生命周期 系统采购 可行性研究 系统分析师 可行性研究报告 系统分析 数据流图 决策表 决策树 系统流程图 数据字典
可行性通常使用几个不同的方面进行度量，比如组织 为实现新系统是否已有或需要购买硬件、软件，实现 新系统的人员需求；新系统是否需要和组织的其他已 有系统配合；新系统的估计效益是否大于估计费用， 等等。
Sentence Explanations
The objective of data collection is to gather information about the work being performed in the system under study. The data collection process attempts to ascertain what resources users need to better perform their jobs. Later in this phase, the data collected should suggest some possible solutions.
vocabulary
Cost/Benefit Analysis tangible benefit intangible benefits system specifications request for proposal request for quotation vendor rating system benchmark test project management software post-implementation review 费用/效益分析 可回收效益，有形 效益 无形效益 系统说明书 招标书 投标书 厂商评分系统 基准测试 项目管理软件 系统完成复审
决策表用于定义过程和概要描述系统中一个步骤的决策过 程。
Sentence Explanations
Checcklists are often developed for important matters such as the goals of the system and the information needs of key people in the system.
检查表通常用于系统目标和系统中关键人员的信息需求一 类的重要内容。
Sentence Explanations
The system design phase primarily consists of developing a model of the new system and performing a detailed analysis of the expected benefits and costs.
数据字典用于描述数据库或其他计算机系统使用的数 据特性。它包括每个数据条目的名称和描述，数据存 储的文件，允许的数据类型和大小，输入格式的限制 （允许的数据位数，允许的字符等）以及拥有修改数 据规范权限的人员。
Sentence Explanations
Some benefits can be computed easily by calculating the amount of labor the new system will save, the reduction in paperwork it will allow, and so on. These gains are called tangible benefits, because they represent quantifiable dollar amounts.
数据流图表明系统各部分活动间的关系以及每个活动流入 流出的数据和信息流。
Sentence Explanations
Decision tables are useful for identifying procedures and summarizing the decision making process for one step of a system.
用于系统分析员建模新系统的工具有流程图，输入/输 出设计和数据字典。系统流程图阐述系统中发生的操 作——类似于数据流图，但更加注重每个处理过程。 输入和输出设计表明输入输出的格式和系统的外观— —比如输入屏幕和打印的报表。
Sentence Explanations
A data dictionary is used to describe the characteristics of data used in a database or other type of computer system. It includes such information as a name and description for each piece of data, as well as the file that data will be found in; what type and size of is allowed; any restrictions on the format of input (within a certain range of numbers, just certain characters of the alphabet, etc.); as well as who has the authority to update that data's型和进行详细的预计 效益和费用分析2部分组成。
Sentence Explanations
Some of the tools a system analyst can use to model the new system are system flowcharts, input/output designs, and a data dictionary. System flowcharts illustrate operations that occur throughout the system—similar to a data flow diagram, but much more specific regarding each individual process. Input and output (I/O) designs show in what form input to, and output from, the system will appear—for example, input screens or printed reports.
在深入探讨SDLC的每一步前需要认识到SDLC的6个步 骤并不总是严格地按顺序一步接着一步进行。例如。 系统分析和设计就经常交织在一起。
Sentence Explanations
When a proposal for a new system or system modification is submitted, one of the first steps is to conduct a preliminary investigation, or feasibility study. The purpose of this investigation is to define and evaluate the problem area at hand relatively quickly, to see if it is worthy of further study, and to suggest possible courses of action.