Database abstractions: aggregation and generalization
ACM Transactions on Database Systems (TODS)
A relational model of data for large shared data banks
Communications of the ACM
An algebra of relations for machine computation
POPL '75 Proceedings of the 2nd ACM SIGACT-SIGPLAN symposium on Principles of programming languages
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The data models that are presently being proposed for the conceptual level of database description all have a feature in common with predicate calculus: both in the declaration and in the manipulation of data structures a distinction is made between names denoting individuals (values, objects, entities, etc.) and names denoting predicates (types of objects, of relationships, of associations, etc.). This distinction makes it impossible to conceive names such as 'male' or 'scheduled' in one case as a predicate and in another case as an individual. A single name category data model has been developed in order to eliminate the need for such distinctions; it is the purpose of this paper to investigate potential benefits and problems of the approach and thereby to provide more insight into data models with multiple name categories. Additional effectiveness and data independence are shown to be among the benefits of the single name category approach, while the main problem is one of lack of structure.