Entity Relationship Index Cardinality Participation Degree Structural Constraints of Kind (Min, Max)
Institute of Information Theories and Applications FOI ITHEA
The basic conceptions of the model „entity-relationship” as entities, relationships, structural constraints
of the relationships (index cardinality, participation degree, and structural constraints of kind (min, max)) are
considered and formalized in terms of relations theory. For the binary relations two operators (min and max) are
introduced; structural constraints are determined in terms of the operators; the main theorem about compatibility
of these operators’ values on the source relation and inversion to it is given here.