什么是系统工程（字幕）25

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我们来看这个用例规约怎么写

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就按照我们前面讲的

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那些内容来写嘛

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执行者

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这个主，这几个辅

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那这个就跟前面的那个系统用例图是对应的了

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对吧

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这是照抄的

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下面就是要

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自己加上去的，前置条件

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后置条件

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前置条件

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是一个背景条件

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就是说

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即使目前蒸馏水这个用例没有在运行

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这个条件依然可以检测，哪一个

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就这个

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背景条件

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后置条件，就是

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这个用例

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要算成功

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那应该是处于什么状态下，这个系统

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这是后置条件

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再往下走

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就是涉众利益了

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这是

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相当于什么，上游

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这是执行者

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这个操作的村民是执行者

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村长

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这是一个比较大的涉众

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但他自己可能不一定操作的

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还有热源厂商

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这可以看作是下游

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或者是这个

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信息的主人

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因为你用的热源

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如果说，我们这个系统故意歧视他的热源

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故意，后面在这个设计上

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针对某种热源

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我就故意搞得

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故意不好好做

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那不把那个厂家给坑了吗

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对不对

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还有，我故意

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我们系统故意去坑这个水分配系统

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把它搞坏

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那后面这些人怎么样

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他也不高兴

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他的利益也会受到损害

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涉众利益

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那我们看，基本路径

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接通水源，调节流量

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这跟我们那个前面的活动图

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是类似的

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只不过把活动图里面的步骤搬到这里来

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那我们加了一些后面这个

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请求水分配系统接受净水

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判断要排空残渣

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这是基本路径

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扩展路径就是有意外的

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比如说

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要是没达到呢

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显然没达到

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是

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发生了很多的，对吧

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没达到

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就直接转到7

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如果没达到需要排空

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那就当前循环就结束了

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就下一个循环

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这是

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扩展路径的条件，这是做法

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字段列表

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就是这个地方

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一个转换的

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输入是污水、热

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输出，净水、残渣

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那么这跟我们前面那个

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画的那个活动图

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那个输入输出是一样的

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就照抄就可以

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照搬就可以

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那这里有一个业务规则

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什么叫足够分配值

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什么叫需要排空值

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如果比较复杂

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比如说，你这个值可能是根据你的这个

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蒸馏器的大小

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还有呢，你的那个水分配系统的管道的粗细

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对吧

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还有那进水的什么粗细什么之类的

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它可能有规格

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有个表格

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如果是这么大的

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那应该是

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多少

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如果是这么大的

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应该多少

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残渣也是一样的

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可能跟很多因素有关

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如果在这里放不下

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你就可以，参见某某某文档的

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里面的某某表格这样写

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质量需求，就是

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包括速度、容量等等

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这个就是做到多好

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那我们可以，比如，平均每小时能处理多少污水

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这个相当于速度

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要快

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对吧

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不能说一天处理一公斤

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那不是瞎搞吗

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还有呢，这个纯度

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你出来这个水质量怎么样

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对吧

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这是质量需求

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设计约束

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无，没有，你爱怎么做怎么做

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如果说有

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你可以怎么加

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比如说

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涉众要求

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一定要用某某品牌的热源

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否则不给钱

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那这里要写

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必须要用某某品牌的热源

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但是必须来自什么

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来自涉众的要求

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包括这个厂家的

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包括那个什么那个

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公益团体的

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包括村民的

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对吧

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比如说，村民就是说

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我们这边就是流行某某热源，那个便宜

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而且是对方厂家免费赠送的

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那就要求你一定要用这个热源

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否则你这个系统就

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不适合他的需要

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设计约束

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一定是来自涉众的

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不能来自我们自己

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不能来自

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设计这个东西的设计团队

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设计团队是不存在的

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我们前面讲愿景的时候也说嘛

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我们做需求的时候

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要把这个

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研发团队看作是死人

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这系统谁做的

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外星人做的

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我们只需要提需求，功能、性能，就行了

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剩下的外星人帮我们搞定

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那用例规约

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就这样来

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这样来写