hat a system must work within to satisfy an organizations objectives and solve a set of problems.
需求是一个系统必须具备的功能或品质。需求指出了系统拥有的可估量和可验证的功能，同时约定系统必须满足客户的目标，解决相关的问题。
There are two types of requirements。 Functional requirements。 Non-functional requirements e.g. performance/reliability， interfaces， design constraints， etc.
有两种类型的需求：
l 功能性需求。
l 非功能性需求。象性能/可靠性，界面，设计约束等。
Requirements elicitation is defined as “the process of identifying needs and bridging the gaps among the involved communities for the purpose of defining and distilling the requirements to meet the constraints of these communities”[SEI]. RE involves social and communication related issues as well as technical issues.
需求捕获可定义为：需求捕获是两个有关团体相互沟通，识别需要的过程。两个团体通过这个过程提取、定义需求，来约束两个团队。需求捕获既涉及技术问题，也涉及社会交往问题。
RE can be further broken down into the activities of fact-finding （identification of sources of requirements or stake-holders as we will call them in rest of this document）， information gathering （getting the “wish-list” from all the relevant parties） and integration （documenting & refining the “wish-list” through repeated analysis until it is self-consistent）。
需求捕获可进一步分为查找需求源（识别需求的提出人或则称之为风险承担者，即产品涉及其利益的人，在该文档其余部分将继续使用风险承担者这个词），网罗信息（收集各方面人员的对产品的要求，得到“期望列表”）和整和（反复分析“期望列表”直到前后一致，得到文档化，提炼后的“期望列表”）等活动。
The product from the elicitation phase is a subset of the goals from various parties. The remainder of the requirements engineering process concerns the validation of this subset to see if this was what the sponsor and the users actually intended.
在捕获阶段得到的“期望列表”是各方面期望的一个子集。需求工程中的其余活动关注于验证这个子集是否满足客户和使用者的意愿。
下一章将介绍需求捕获的问题和需求捕获的过程（待续）