工作流技术导论——Petri Net进阶
题目
A secret project by the government (let’s call it Project X) will be executed by one person and consists of 6 tasks: A, B, C, D, E, and F. Figure 2.28 specifies the order in which the tasks need to be executed (precedence graph, cf. PERT/CPM). A possible execution trace is for example ABDCEF.
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Model the project in terms of a classical Petri net.
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How does one model so that E is optional?
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How does one model so that D and E should be executed consecutively, that is, B and C are not allowed between D and E?
答案
- 第一小题使用古典的Petri net，直接按照题目中所给的图画出即可
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第二小题要求是需要将TaskE设置成可选项，因此在TaskD完成之后的缓冲区，多设置一个变迁，即可不完成TaskE达到TaskF前的缓冲区
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第三小题要求TaskB和TaskC不能在TaskD和TaskE之间完成，因此我们多设置了一个缓冲区，使得BCD变迁都需要在该缓冲区有token，而且BC执行完成后会生成一个token返回到该缓冲区，而D则需要在完成E之后才会返回一个token到该缓冲区中