DLOB M2: Conceptual Data Modelling · Weak Entity Sets

Consider the diagram to the right.

The entity set "Transaction" should be considered as a weak entity set, because a "Transaction" can not exist without an "Account" entity.The "Log" relationship set serves as an identifying entity set. The attribute "transaction number" is the discriminator of the "Transaction" entity set.

Express these facts in the diagram:

  1. Hold the mouse down for a second on the "Transaction" entity set to open the popup menu. In the popup menu choose "Type > Weak".
  2. Open the popup menu for the relationship set "Log". Choose "Type > Identifying".
  3. Hold the mouse down for a second on the connection between "Account" and "Log" to open the popup menu. In the popup menu choose "Cardinality > 1".
  4. Open the popup menu for the connection between "Account" and "Log". Choose "Mark as total participation".
  5. Open the popup menu for the attribute "transaction-number". Choose "Discriminating".

Click at "Compare with Solution" to see whether your diagram is correct, and to get a description of the solution.

Source: http://www.cs.sfu.ca/CC/354/zaiane/material/slides/Chapter2/sld024.htm

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