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Lecture Notes in Computer Science
An extended entity-relationship model concentrating nearly all concepts of known \semantic" data models and especially allowing arbitrary user de ned data types is introduced. The semantics of the model is described purely in algebraic terms mainly based on the notions of signature, algebra and extension. On this basis a calculus making intensive use of abstract data types is de ned and employed for the formulation of typical integrity constaints like functional restrictions and key speci cations.doi:10.1007/3-540-50939-9_137 fatcat:fgeiznfxhbhujbmnn3ineupdrq