3.4.12. Completeness constraint

  • Total specialisation
    • Every entity in the superclass must be a member of atleast 1 subclass
    • Double line (as ER)
  • Partial specialisation
    • Some entites may belong to atleast 1 subclass, or none at all
    • Single line
  • Yields 4 possibilities
    • (Total-Dis, Total-Over, Partial-Dis, Partial-Over)