er time
在需求的問(wèn)題上有這樣一些觀點(diǎn)：
1、到達(dá)需求的完整性會(huì)束縛系統(tǒng)設(shè)計(jì)。
2、需求分析和驗(yàn)證比較困難。
3、改變需求會(huì)消耗額外的時(shí)間。
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.
許多未被發(fā)現(xiàn)的需求錯(cuò)誤被傳遞到生命周期的后繼階段，在后繼階段更正這些錯(cuò)誤將花費(fèi)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
需求捕獲的問(wèn)題可以分為三類：
范圍的問(wèn)題，需求陳述的信息過(guò)多或是過(guò)少。
理解的問(wèn)題：用戶不完全理解自己的需要需求分析人員對(duì)于問(wèn)題域缺乏足夠的知識(shí)忽略一些“明顯”的信息。
不同用戶的看法有沖突語(yǔ)句含糊和無(wú)法測(cè)試的需求。例如“用戶界面友好”或“高性能”
需求不穩(wěn)定的問(wèn)題。例如需求本身的改變/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.
捕獲需求的范圍應(yīng)比較寬廣，這樣可以為目標(biāo)系統(tǒng)制定一個(gè)適當(dāng)?shù)倪吔?。捕獲需求注重于產(chǎn)生需求而不是設(shè)計(jì)活動(dòng)。捕獲需求一般從組織結(jié)構(gòu)和上下文范圍開(kāi)始分析，來(lái)界定目標(biāo)系統(tǒng)的邊界。要避免上下文范圍問(wèn)題可能導(dǎo)致的不完全，不可用和無(wú)法驗(yàn)證的需求。
Elicitation must focus on creation of requirements， not design activities in order to adequately address the users‘ concerns. Focus on broader design activities improperly