entity-relationshipmodeling
EER Subtyping differences in symbol placement
I have a simple question regarding the use of sub-type symbol in the EER model. I gave example diagrams bellow. My question is what is the difference between using the subtype symbol "U" in the line from parent to subtype or from subtype to parent, for more clearity, see example diagrams bellow.
Solution
I couldn't find any reference using the second notation. Unless otherwise defined, we could choose to read it as equivalent to the first, though it challenges the reader to determine why a different notation is used. For the sake of effective communication, I would recommend honoring the existing convention.
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