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今天呢，我们来看一个用语

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非功能需求

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这个算不算糊涂用语

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这是来自一个学员的问题

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他说，之前你写的书里面

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把需求分为功能需求、非功能需求、设计约束

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第二版就把非功能需求改成

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质量需求了

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那非功能需求到底是不是

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糊涂用语

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那我们先说一下结论

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非功能需求属于

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属于模糊用语

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不过这个模糊是表达上的模糊

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它来源于历史习惯

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如果我们继续使用的话

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害处是比功能模块、用户需求之类的要小

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非功能需求

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这个用语模糊在哪里呢

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模糊在

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你看，我们

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这样写，需求分为功能需求、非功能需求、设计约束

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这是我们

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刚才那个表述嘛

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那我们看，假设把需求看作全集

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功能需求是它的一个子集

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另外一个子集叫非功能需求

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那你看从这个

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含义上，非功能需求

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意思是功能需求的非

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就是它的补集嘛

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对不对

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全集里面

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除了功能需求之外

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那个集合，补集

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那既然是补集

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那应该是，功能需求和功能需求的补集

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并在一起就得到了需求

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那就没有设计约束了

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对不对

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这两个加在一起就已经得到了整体的嘛，这功能需求

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剩下的非功能需求，没有了

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设计约束没有了

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模糊在这里

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但是这个模糊

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并不是我创造的

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那么也肯定是很久以前

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我从书里面学来的

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因为过去的教材等等

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都这么讲的

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你看，我摘几本

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我手上有的中文的

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中文或中译本的书

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我们看一眼

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那这里只是展示说书里面有这个内容

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不评价这个书的质量好坏

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不要误解我推荐或者不推荐这本书

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没有任何推荐或不推荐的意思

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比如说，2019年这个《软件工程》

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这是翻译的

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你看

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这里面写，有功能需求

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有

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非功能需求

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设计约束，几个并列

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对吧

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它这里把质量需求跟非功能需求

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这两个是对等的

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这两个是一个意思

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你看，它也是这样表达的

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功能需求

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非功能需求、设计约束

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机械工业出版社

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2018年

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这个也是翻译的，软件工程导论

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并列的，功能需求

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非功能需求

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设计约束，上一页是功能需求

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非功能需求，跟设计约束

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并列的

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这个是Ivar Jacobson

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就是UML的

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创造者之一

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他自己写的这个书

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你看，他这里面是

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把这三个，功能需求、非功能需求、设计约束

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并列

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这是国外的翻译过来的

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那国内的也一样

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你看，这是

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国内的，徐锋写的软件需求最佳实践

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这里也是写

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分为三种类型，功能需求

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非功能需求、设计约束

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这个

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是

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很多时候我们习惯是这样用

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但确实是模糊用语

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那怎么修正呢

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怎么表达更严谨一点

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有这么几个方案，我们来评价一下

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第一个

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我们认为这个设计约束不是需求

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你可以说设计约束不是需求

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但是呢，这个肯定不好了

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因为

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这三个并列在一起

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你不管叫它阿猫阿狗

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叫ABCD

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它就是需求的一种

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它肯定是符合什么

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不这样不行

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什么叫需求

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就是如果不这样

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就会损害设计的利益

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那设计约束确实是需求的一种

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比如说

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我们这个界面

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左上角一定要

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有一个章

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这个章的颜色一定是这样的

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形状

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必须这样的

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为什么

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因为是政府的规定

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那个章已经规定好了

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这个式样，你不要自己乱发挥

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不能说，这个不漂亮

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我给你搞一个

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我找那个

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设计师去搞更漂亮的界面

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不行的

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人家规定格式就是这样的一个格式

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所以呢

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这个确实是属于什么

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不这样不行

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或者说我们

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数据库

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一定要用Oracle

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为什么呢

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因为我们的客户

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他以前买了很多Oracle的产品

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所以呢他数据

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放在Oracle上面

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来保存

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对他来说是比较划算的

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不用重复再买购买类似的产品

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它是

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来自涉众的要求

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不这样不行

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否则就会损害涉众的利益

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对不对

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不是来自

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开发团队

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不是说，因为我们对Oracle比较熟

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所以那个，不是这个，来自涉众的

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跟我们开发不开发这个没有关系的

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跟我们开发团队的特点没有关系

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所以呢，这个是不合适

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第二种就是

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我们可以认为

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设计约束

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是非功能需求的一种

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这个可以

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这样就是可以的

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需求等于功能需求+非功能需求

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而设计约束是非功能需求的一种

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把它放到下层了

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不再跟之前那个并列

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对不对

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但这个有什么不好

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就是它变成一种什么，这个非功能需求

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就变成一个口袋的一个名字

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功能需求

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剩下的，非功能需求

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口袋的

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人有男人

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还有不是男人的人

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这个可以

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但这个肯定是不好的

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因为他放一个口袋在那里

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把这种乱七八糟的装进去了

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那说明什么

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我们没有把它分清楚

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就像我们物理学一样的

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物理有几种力

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有这个力

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然后你拿一个口袋

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非什么什么力

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剩下的都叫非什么什么力

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那不好

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第三种就是说把这口袋命名去掉

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改为这种比较明确的命名

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就像刚才讲的

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比如说，需求等于功能需求、质量需求、设计约束

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这样可以

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但这个也是冗余

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你看

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写什么需求

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需求，没有必要嘛

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对吧

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能不写就不写

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我的意见就是直接功能、性能、设计约束

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就行了

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能少写几个字就少写几个字

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那这里的性能就包含了我们以前的

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所谓非功能需求里面的内容

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包括速度、容量

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可靠性、可用性等等

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在这里面

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我们都统一叫性能

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那我推荐是这样用

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设计约束这个设计要不要删掉

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00:09:23,602 --> 00:09:23,811

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这个好像不好删

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因为这个是设计时候的约束

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不是别的约束

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是在实现过程中

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出于涉众利益

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不得不遵守的

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比如说，就像刚才讲的

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数据库一定Oracle

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为什么，人家单位

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他就这样要求的

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因为这样要求对他有利

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如果你光写约束的话

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很容易跟业务规则搞混在一起

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00:09:58,788 --> 00:09:59,025

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而业务规则属于什么

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属于功能的部分

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它是核心域的概念

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比如说，计费的规则

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它是附属在计费里面的

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计费有个计费的规则

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是一个公式

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这个费加这个费加这个费乘以多少

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不能光写约束，要设计约束

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在设计过程中不得不遵守的约束