An Extended Entity-Relationship Model

This text presents a comprehensive introduction to an
extended                     Entity-Relationship model both on a conceptual and
on a formal, mathematicallevel. In addition to the
primitives given by the data model the text         introduces a
language for the formulation of constraints in order               to
restrict database states to consistent ones. The text
explains an      implementation of the approach chosen in the
logic programing language         PROLOG and discusses in this
context the computational power of the proposedcalculus.
The extended Entity-Relationship calculus is used to                     define
the meaning of the relational query language SQL. A nice
feature of the approach is that it becomes possible to prove
language properties on a sound mathematical basis.