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Andrew Johnson APS Engineering Support Division

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Explain the distinction between condition-defined and user-defined constraints. Which of these constraints can the system check automatically? Explain your answer. Answer: In a generalization–specialization hierarchy, it must be possible to de- cide which entities are members of which lower level entity sets. In a condition- defined design constraint, membership in the lower level entity-sets is evalu- ated on the basis of whether or not an entity satisfies an explicit condition or predicate.User-defined lower-level entity sets are not constrained by a member- ship condition; rather, entities are assigned to a given entity set by the database user. Condition-defined constraints alone can be automatically handled by the sys- tem. Whenever any tuple is.