''EntityRelationshipModeling '' by BernhardThalheim

http://images.amazon.com/images/P/3540654704.01._SCMZZZZZZZ_.jpg

[ISBN 3540654704] It's a consolidation of much of the research work that has gone on since Chen's introduction of the ER model.  It's quite powerful, but most of the literature is rather formal and a bit difficult for non-logicians to parse (thus far).

More information:
* Book available at discount -- http://www.informatik.tu-cottbus.de/~thalheim/HERM.htm
* Postscript Downloads of accompanying material -- http://www.informatik.tu-cottbus.de/~thalheim/slides.htm

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See also EntityRelationshipDiagram