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@inproceedings{DBLP:conf/er/ScheuermannSW79,
author = {Peter Scheuermann and
Gerd Schiffner and
H. Weber},
editor = {Peter P. Chen},
title = {Abstraction Capabilities and Invariant Properties Modelling within
the Entity-Relationship Approach},
booktitle = {Entity-Relationship Approach to Systems Analysis and Design.
Proc. 1st International Conference on the Entity-Relationship
Approach},
publisher = {North-Holland},
year = {1979},
isbn = {0-444-85487-8},
pages = {121-140},
ee = {db/conf/er/ScheuermannSW79.html},
crossref = {DBLP:conf/er/79},
bibsource = {DBLP, http://dblp.uni-trier.de}
}
The E-R model provides a good framework for the modelling of a conceptual schema for a database. One drawback of the original model was its lack of capability to express abstractions. We show in this paper that not only aggregates and generalization, but also relationships between relationships, can be incorporated quite naturally in the original model.
Next, we further enhance the E-R model with a number of intensional constructs necessary to express several elementary integrity constraints. In this class of intensional constructs, we include partial and total relationships and weak relationships of two types. Associated with these intensional constructs are different invariant properties which must be preserved during update operations. We show that the type of update operation and the type of invariant property (i.e. intensional construct) uniquely determine the way updates may propagate through the database. Finally, we show that within the module concept where data and operations are defined together, we also have the capability to automatically enforce the sequence of operations due to invariant properties.
