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Ok we're doing some ER stuff in class and I'm confused on specialization.

Lets say we have an entity A which has a disjoint specialization into A1 and A2. Another entity B has a relationship 'has', every B has one A1 and every B has any number of A2.

I can't quite figure out how to draw it.

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To clarify;


I have a single relationship 'HAS_A' from 'B', however 'A1' and 'A2' both of which are related to B through 'HAS_A' have different cardinality and participation. Does this mean I have to create two 'HAS_A' relationships, one between B and A1 and one between B and A2 or is there some way to do it with a single relationship.

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