On the satisfiability of dependency constraints in entity-relationship schemata
Information Systems
Fundamentals of database systems (2nd ed.)
Fundamentals of database systems (2nd ed.)
Description logics for conceptual data modeling
Logics for databases and information systems
The entity-relationship model—toward a unified view of data
ACM Transactions on Database Systems (TODS) - Special issue: papers from the international conference on very large data bases: September 22–24, 1975, Framingham, MA
Enhancing the ER model with integrity methods
Journal of Database Management - Special issue on information modeling methods
Fundamentals of Cardinality Constraints
ER '92 Proceedings of the 11th International Conference on the Entity-Relationship Approach: Entity-Relationship Approach
Extending ER Model Clustering by Relationship Clustering
ER '93 Proceedings of the 12th International Conference on the Entity-Relationship Approach: Entity-Relationship Approach
Multirelational Semantics for ExtendedEntity-Relationship Schemata with Applications
ER '02 Proceedings of the 21st International Conference on Conceptual Modeling
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Entity Relationship schemas include weak entity types, whose entities are identified by their inter-relationships to other entities. During the translation of the EER schema into a logical database schema, the weak entity types are either translated into logical units of the database (a relation or a class), or are embedded as attributes of other logical units. Formal studies of EER schemas either ignore the presence of weak entity types, or simplify their dependency structure. The presence of weak entity types in an EER schema may be problematic: A weak entity may not be easy to identify because it may be related to other weak entities in various ways, thus causing problems in schema comprehension, as well as in mapping it to a logical database schema. We claim that the presence of weak entity types in an EER schema belongs to an intermediate design stage, but the final EER schema must not include such entity types. We introduce an algorithm for resolving the status of weak entity types, following user directions. If the directions are legal, the algorithm yields an EER schema without weak entity types. The advantage of our approach is twofold: First, the translation of an EER schema into a logical database schema can be fully automated. This is essential for upgrading the EER model to support full database management. Second, it enables a fully formal study of the EER model.