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14. UML > Symmetric Relationships

Symmetric Relationships

You said that associations provide a more symmetric viewpoint on a situation than pointers in most programming languages. Can you elaborate?

James: In the real world, relationships are relationships. They’re not usually encapsulated to only work in one direction. Occasionally they are, but mostly if A is related to B, then B is related to A.

Is it a bidirectional relationship?

James: Well, it’s a relationship. Relationships are inherently bidirectional. Mathematical relations are bidirectional. Even saying bidirectional implies that one is thinking of pointers. Relationship is relationship. The things are related and neither side takes precedence, maybe that’s how to say it. Bidirectional doesn’t mean symmetric, of course—man bites dog is different from dog bites man.


  

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