8. Define identifying properties for object, role and relationship types

• Each design information must be “labeled” one property type

  • A property type used to refer to the types instances

• Identifiers can be often unique

• Some times identifiers and unique values are different:

  • e.g. in our example of DFD:
    • Process ID should be the unique (inside the DFD hierarchy)
    • Process name could be the identifier

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