问题
Consider the following (abstract) situation:
Two entities. There are two aggregation relationships between the two entities.
The diagram looks like this:
I know this might sound vague, but is there anything wrong with this picture?
I mean, are there any (obvious) problems that could arise from this kind of design?
Or am I being paranoid and there's absolutely nothing wrong with two (or more) aggregation relationships between two entities?
回答1:
For me there is nothing wrong in such design. Your Entity2 will have a different role in each context that's all.
回答2:
Nothing wrong with the diagram. Here is a more meaningful example.
-Kenji
回答3:
As long as the relationships are fulfilling really different roles (as you indictated by the numbering) I think it is a good approach, as you make them explicit.
Otherwise you could make use of the cardinality:
来源：https://stackoverflow.com/questions/23105732/two-or-more-aggregation-relationships-between-two-entities