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Fig. 7.13 Merge EER models by subtype relationship
the higher level of participation has absorbed the lower level of participation in the
transformed schema with a new entity and relationship created, no alteration of data
semantics is necessary.
Case 2: Two relationships have different semantics but with an intersecting re-
lationship. The verification of this step is to identify two relationships that have
different semantics but with an intersecting relationship. The schema which has
overlapping relationships of different kinds of semantics would naturally dominate
these schemas by assigning an overlap generalization relationship to its intersecting
schemas. Hence, information about its original semantics and relationships should
both be preserved (Fig. 7.13 ).
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