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需求捕获指南(二)—需求捕获的问题及过程

4 Issues in Requirements Elicitation

4、需求捕获的问题

Eliciting requirements need not be like pulling teeth … but sometimes it is. The problem is lack of preparation by the software engineer and lack of interest by the organization or person requesting the work. One would think that the customer would be very interested, since the software to be built solves a problem that the customer has. But often, the customer expects the developer to "know" and has little interest in spending time doing "computer stuff." A mistake, no doubt, but reality none the less. One can use the Requirements Elicitation Success Measurement checklist to identify where your project stands as far as the success of the requirements elicitation is concerned. For this checklist, the more questions that elicit a negative response, the higher the risk that the requirements elicitation will fail.

需求捕获不象是拔牙…但也对照类似。常见的问题是,软件工程师短缺筹备,同时必要该产品的组织或小我短缺兴趣。一样平常大年夜家都邑觉得客户会对产品很感兴趣,由于该产品会办理客户面临的问题。但平日客户盼望开拓职员已经知道相关常识或不乐意消费光阴为软件产品供给根基材料。无疑,这些不雅点是差错的 ,然则客不雅存在的。可以应用需求捕获列表来验证你的项目在需求捕获方面进展若何。在这个列表中,越多问题的谜底是否定的,那么需求捕获掉败的可能性就越高。

Requirements engineering consists of activities like requirements elicitation, specification and validation.

需求工程包括的活动有需求捕获,需求定义和需求验证。

The hardest single part of building a software system is deciding what to build… … No other part of the work so cripples the resulting system, if done wrong. No other part is more difficult to rectify later.

开拓软件系统最艰巨的部分在于确定要开拓什么。而这一部分又最可能导致系统的掉败,最难以在后继的事情中加以纠正。

Issues involved in this problem area include:1. Achieving requirements completeness without unnecessarily constraining the system design 2. Analysis and validation difficulty 3 Changing requirements over time

在需求的问题上有这样一些不雅点:

1、到达需求的完备性会束缚系统设计。

2、需求阐发和验证对照艰苦。

3、改变需求会耗损额外的光阴。

Many requirements errors are passed undetected to the later stages of the life cycle and correcting those errors during or after implementation phase is found to be extremely costly.

许多未被发明的需求差错被通报到生命周期的后继阶段,在后继阶段更正这些差错将花费更多。

Problems of RE can be grouped into three categories:。 Problems of scope, in which requirements may address too little or too much information。 Problems of understanding o Users have incomplete understanding of their needs o Analysts have poor knowledge of problem domain o Ease of omitting “obvious” information o Conflicting views of different users o Vague and un-testable requirements e.g. “user friendly” & “robust”

Problems of volatility i.e. changing/evolving nature of requirements

需求捕获的问题可以分为三类:

范围的问题,需求述说的信息过多或是过少。

理解的问题:用户不完全理解自己的必要需求阐发职员对付问题域短缺足够的常识轻忽一些“显着”的信息。

不合用户的见地有冲突语句暧昧和无法测试的需求。例如“用户界面友好”或“高机能”

需求不稳定的问题。例如需求本身的改变/拓展。

Elicitation techniques need to be broad enough to establish the boundary conditions for the target system, and yet focus on creation of requirements as opposed to design activities. RE must begin with an organizational and contextual analysis to determine the objectives and boundary of the target system. Avoiding contextual issues may result in incomplete, unusable and un-verifiable requirements.

捕获需求的范围应对照宽广,这样可以为目标系统拟订一个适当的界限。捕获需求重视于孕育发生需求而不是设计活动。捕获需求一样平常从组织布局和高低文范围开始阐发,来界定目标系统的界限。要避免高低文范围问题可能导致的不完全,弗成用和无法验证的需求。

Elicitation must focus on creation of requirements, not design activities in order to adequately address the users‘ concerns. Focus on broader design activities improperly emphasizes developers’ issues over users‘ needs and may result in poor requirements. Requirements in the form of high-level design run the risk of being un-verifiable by the user, as user might not understand the design language. There are at least three broad contexts concerned to RE:

捕获专注于需求而不是设计,这是为了充分懂得用户的关注点。专注于设计会不适当的强调开拓问题而轻忽用户的必要,导致掉败的需求。需求中掺杂了设计,会应用户无法验证需求,同时用户可能无法理解设计方面的说话。在需求获取中有三个较大年夜的领域必要分外留意:

Organization o Submitters of the input to the target system o Users of the output of target system o Ways in which target system will change the organization’s means of doing business

组织机构目标系统输入信息的供给职员应用目标系统输出信息的用户目标系统可能改变组织机构的营业流程。

Environment o Hardware and software constraints imposed on the target system o Maturity of target system‘s domain o Certainty of the target system’s interfaces to the larger system o The target system‘s role within a larger system

情况目标系统的软,硬件限定。

目标系统问题域的成熟程度。

目标系统的界面与组织现有大年夜部分系统界面风格同等。

目标系统与组织现有其他系统的关系。

Project o Attributes of different stakeholders e.g. management style, domain/computer experience o Constraints imposed e.g. cost, quality, timelines, etc.

项目不合风险承担人的特征,如治理风格,问题域/谋略机履历。

其他约束前提,如资金,质量,光阴刻日。

5 Requirements Elicitation Process

5、需求捕获历程。

Following process graph shows the “should-be” RE process, which was created during a sample requirements elicitation process study. This gives a bird‘s eye view of the proposed business process model, which is a refined RE process.

下面的历程图显示了“应该”的需求捕获历程,它滥觞于实际的一个简单的需求捕获义务。它给出了建议的历程模型,也是一个正确的需求捕获历程。从这幅图上,你可以对需求捕获历程有个周全的熟识

下一章将先容需求捕获的阶段组成(待续)

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