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Entity relationship diagrams doubt

  1. Oct 16, 2013 #1
    I am doing a project of an entity relationship model and a doubt came: Should repeated attributes of the entities be shared? Or I must reproduce these to every entity? In another words, if two of my entities are books and magazines, shall I have a single publisher attribute, or one for each?
  2. jcsd
  3. Oct 16, 2013 #2


    Staff: Mentor

    What if you have some other entity, such as publication, with books and magazines as subclasses (or subentities)?

    Whatever attributes that both books and magazines have in common could be defined in the publication entity, and the attributes that books and magazines don't share would go in one or the other of these entities.

    That's just my take...
  4. Oct 16, 2013 #3
    True, that's a better solution. On a side note, anyone here has any experience using yuml? If someone does, the problem is that I don't know uml, so I tried to make my diagram through modifications of given samples in the yuml website. But I wasn't able to combine the two geometric shapes that I wish simultaneously. That's because a rectangular box is available in the Class Diagram Samples and the oval shape is available in the Use Case Diagram. But both doesn't work simultaneously in any of the two kinds of diagrams Example: (Register)>(Confirm Registration) is in the "Use case diagram" and [Customer]->[Billing Address] is in the "draw class diagram"
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