Analysis of binary relationships within ternary relationships in ER modeling
In this paper, we discuss which binary relationship cardinalities are permitted within ternary relationships, during ER modeling. We develop an implicit Binary Cardinality (IBC) rule, which states that, in any ternary relationship, the cardinality of any binary relationship embedded in the ternary, is many-to-many when there are no explicit constraints on the data instances. We then present an Explicit Binary Permission (EBP) rule, which explains and enumerates all permitted binary relationships for various cardinalities of ternary relationships. Finally we present an Implicit Binary Override (IBO) rule, which states that the implicit binary cardinalities can be constrained in a ternary relationship by explicit constraints imposed by a binary relationship. We also detail how the cardinalities within the ternary are altered as a single binary, and then multiple binary relationships are imposed.
KeywordsCardinality Constraint Potential Combination Binary Constraint Entity Relationship Explicit Constraint
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