Are there arguments against ER models and their extensions


Problems related to cardinality constraints

Cardinality constraints are rather complex constraints. They combine referential constraints and functional dependencies. Referential constraints are specific inclusion constraints. The nature of cardinality constraints is well understood in the case of binary relationship types. In this case, lookup notation and participation notation can be mapped to each other. For relationship types of arity higher than 2, the two notations cannot be mapped to each other.

Furthermore, often weak, logical and strong semantics are used together without noticing that. Weak semantics denotes the "usual" case. Strong semantics require that both the lower and upper bound must be met. Logical semantics denotes the cases that occurrence numbers below the lower bound and above the upper bound are forbidden.


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