但是大概的意思是肯定沒錯的。如果具體有哪句不是很明白的話，妳就留言給我吧。
A perfectly rational person is one who always has a good reason for what he does. Each step taken can be shown to be the best way to get to a well defined goal.
壹個理性的人，應該對他自己所作所為有很好的理由。每壹個步驟都是達到明確目標的方法。
However, to many observers, the usual process of designing software appears quite irrational.
但是，根據多個觀察研究，設計軟件的壹般流程往往是不理性的。
Programmers start without a clear statement of desired behavior and implementation constraints.
沒有清晰明確“必須行為”和“執行約束”前，程序員就開始動手編程。
They make a long sequence of design decisions with no clear statement of why they do things the way they do.
他們都了解自己為什麽要這麽做，就急於動手寫了壹長串的設計決策。
Their rationale is rarely explained. Many of us are not satisfied with such a design process.
他們很少解釋基本原理。我們很多人對這樣的壹個設計流程並不滿意。
That is why there is research in software design, programming methods, structured programming and related topics.
這就是為什麽存在對軟件設計，編程方法，結構編程和相關話題的研究。
Ideally, we would like to derive our programs from a statement of requirements in the same sense that theorems are derived from axioms in a published proof.
最理想的情況是，我們從設計的要求得出編程，就好像從已經得以證明的公理中得出定理。
All of the methodologies that can be considered “top down” are the result of our desire to have a rational, systematic way of designing software.
所有被認為自上而下的方法論都是我們希望通過理性的，系統化的軟件設計方法的結果。
bad news and good news
壞消息和好消息
The bad news is that, in our opinion, we will never find the philosopher's stone.
壞消息是我們認為我們永遠不會找到點金石。
We will never find a process that allows us to design software in a perfectly rational way.
我們永遠不會找到壹個讓我們用完美理性的方法設計軟件的流程。
The good news is that we can fake it.
好消息是我們可以假裝我們找到了這樣的壹個流程。
We can present our system to others as if we had been rational designers and it pays to pretend do so during development and maintenance.
我們向其他人講解我們的系統時，假裝我們是理性的設計者，在開發和維護的過程中，要假裝這壹點，是要付出代價的。
WHY WILL A SOFTWARE DESIGN “PROCESS” ALWAYS BE AN IDEALISATION?
為什麽軟件設計流程總是被理想化呢？
We will never see a software project that proceeds in the “rational” way. Some of the reasons are listed below:
我們從未見到壹個軟件是通過理性的方法設計出來的。其中原因如下所列：
(1) In most cases the people who commission the building of a software system do not know exactly what they want and are unable to tell us all that they know.
在大多數個案中，委托設計軟件程序的人並不真正知道他們需要什麽，也無法將他們所知道的完全告知我們。
（2) Even if we knew the requirements, there are many other facts that we need to know to design the software. Many of the details only become known to us as we progress in the implementation. Some of the things that we learn invalidate our design and we must backtrack.
即使我們知道他們的要求，有許多其他我們需要了解需要知道的方面來設計軟件。很多細節問題，只有在我們到了執行時，才得以知道。有些因素會導致我們的設計無效，所以我們必須回溯。
(3) Even if we knew all of the relevant facts before we started, experience shows that human beings are unable to comprehend fully the details that must be taken into account in order to design and build a correct system.
即使在我們開始之前，可以知道所有相關的時間，經驗表明，人們無法完全理解要設計壹個正確的系統所必須考慮的細節問題。
The process of designing the software is one in which we attempt to separate concerns so that we are working with a manageable amount of information. However, until we have separated the concerns, we are bound to make errors.
設計軟件的流程是我們嘗試分離關註的壹個流程，只有可管理的信息量，我們才能工作。但是，在我們分離關註之前，我們必然會犯各種各樣錯誤。
(4) Even if we could master all of the detail needed, all but the most trivial projects are subject to change for external reasons. Some of those changes may invalidate previous design decisions. The resulting design is not one that would have been produced by a rational design process.
即使我們能掌握所有必須的細節，但是最繁瑣的項目是取決於外部原因而變化。有些原因可能會導致之前的設計決策無效。這樣得出來的設計就不是壹個通過理性的設計流程而設計出來的。
(5) Human errors can only be avoided if one can avoid the use of humans. Even after the concerns are separated, errors will be made.
除非人們不使用，否則錯誤是無法避免的。即使關註能被分離，錯誤還是會出現。