在这里，我有另一个问题聚合和关联。我想学习一些UML的基础知识，所以我开始阅读Martin Fowler的“UML distillation”。我读了两个章节关于类，有一件事，我不能完全掌握我想，这是聚合vs关联。在这本书有这个报价：
In the pre-UML days,people were usually rather vague on what was aggregation and what was
association. Whether vague or not,they were always inconsistent with everyone else. As a result,
many modelers think that aggregation is important,although for different reasons. So the UML
included aggregation (Figure 5.3) but with hardly any semantics. As Jim Rumbaugh says,“Think of it
as a modeling placebo” [Rumbaugh,UML Reference].
正如我从Stack Overflow中读到的这个引用和主题中理解的，我使用的那两个关系中的哪一个是无关紧要的，他们的意思是基本相同，或者是有什么情况下使用聚合而不是关联和/或我不能改变一个到另一个而不改变类图的“意义”？
我问这个，beacuse这本书是从2003年，有些事情可能改变这几年。
