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There are two situation one is double line(recursive), the other is normal

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Could anyone explain why the first one use recursive and the second not?

mko
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1 Answers1

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In the first example, a cow could be both an owner and owned by. For example, a cow could be owned by another cow in a parent-child relationship. A cow could also be owned by a farmer.

In the second example, a student cannot attend another student. There isn't any recursive relationship there.

Eric Hotinger
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  • I may be wrong at the notation, does the double like a full participation notation? please have a look my new question about i t http://stackoverflow.com/q/19781294/456218 – mko Nov 05 '13 at 10:15