10.6. Open/Closed World Semantics
When modeling a business domain, one may take different positions with respect to the completeness of the knowledge captured in the model. The Closed World Assumption (CWA) is the assumption that all relevant facts are known (i.e., appear in the model, either as asserted facts or derived facts) and that all the relevant business rules are known. This is the usual assumption for databases and implies Negation as Failure (the failure to find or prove a proposition implies that it is false).
Consider, for example, the populated ORM model in Figure 10.55(a). There are four students (1001 through 1004), but only two of these (1001 and 1003) are modeled as intelligent. Using CWA, we may deduce that students 1002 and ...
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