9.5. Set-Comparison Constraints
Set-comparison constraints declare a subset, equality, or exclusion relationship between the populations of role sequences. This section compares support for these constraints in UML and ORM. A detailed discussion of these constraints in ORM can be found in Section 6.4.
As an extension mechanism, UML allows subset constraints to be specified between whole associations by attaching the constraint label “{subset}” next to a dashed arrow between the associations. For example, the subset constraint in Figure 9.21(a) indicates that any person who chairs a committee must be a member of that committee. Figure 9.21(b) shows the same example in ORM.
Figure 9.21. A subset constraint in (a) UML and (b) ORM.
ORM has a ...
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