hat a system must work within to satisfy an organizations objectives and solve a set of problems.
需求是一個(gè)系統(tǒng)必須具備的功能或品質(zhì)。需求指出了系統(tǒng)擁有的可估量和可驗(yàn)證的功能，同時(shí)約定系統(tǒng)必須滿足客戶的目標(biāo)，解決相關(guān)的問題。
There are two types of requirements。 Functional requirements。 Non-functional requirements e.g. performance/reliability， interfaces， design constraints， etc.
有兩種類型的需求：
l 功能性需求。
l 非功能性需求。象性能/可靠性，界面，設(shè)計(jì)約束等。
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.
需求捕獲可定義為：需求捕獲是兩個(gè)有關(guān)團(tuán)體相互溝通，識(shí)別需要的過程。兩個(gè)團(tuán)體通過這個(gè)過程提取、定義需求，來約束兩個(gè)團(tuán)隊(duì)。需求捕獲既涉及技術(shù)問題，也涉及社會(huì)交往問題。
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）。
需求捕獲可進(jìn)一步分為查找需求源（識(shí)別需求的提出人或則稱之為風(fēng)險(xiǎn)承擔(dān)者，即產(chǎn)品涉及其利益的人，在該文檔其余部分將繼續(xù)使用風(fēng)險(xiǎn)承擔(dān)者這個(gè)詞），網(wǎng)羅信息（收集各方面人員的對產(chǎn)品的要求，得到“期望列表”）和整和（反復(fù)分析“期望列表”直到前后一致，得到文檔化，提煉后的“期望列表”）等活動(dòng)。
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.
在捕獲階段得到的“期望列表”是各方面期望的一個(gè)子集。需求工程中的其余活動(dòng)關(guān)注于驗(yàn)證這個(gè)子集是否滿足客戶和使用者的意愿。
下一章將介紹需求捕獲的問題和需求捕獲的過程（待續(xù)）