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Distributed Database Systems
semantic integrity constraints: structural constraints
and beha vioural constraints.
Semantic integrity
constraints can be expressed using assertions.
An assertion is a predicate expressing an integrity
constraint that must be satisfi ed by the database.
Assertions can be classifi ed into three different
categories: individual assertions, set-oriented
assertions and assertions involving aggregates.
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The global system catalog stores all the informa-
tion that are required to access data correctly and
effi ciently and to control authorization. There are
three alternative approaches for catalog manage-
ment in a ...