ERM-models synonymy and problems of scheme consistencyand completeness ensuring

In most semantic data models an aspect of the reality can be represented in schema only onceas a structural element or as an integrity constraint. In this case man should care about schemeconsistency and completeness by himself. «Entity - Relationship - Mapping» model (or ERMmodelfor short) gives an opportunity to describe the same aspects of the reality at different levelsin different representations. This feature of the ERM-model allows reflecting any fact at any momentin any form.As a result there can be several forms of the same fact in the scheme at the same moment. Itleads to a problem of consistency between different forms of the same fact. The second problemis scheme reduction. It is a process of scheme transformations up to base concepts, which are necessaryto DBMS-oriented scheme generation. This «normalization» helps to minimize the set ofthe rules for translation into DBMS-language.This paper includes definitions of base and derivative concepts and a demonstration of ERMschemeelements synonymy using graphical notation. Consistency checks can be divided into twogroups: checks based on meta-scheme constraints and checks based on formal systems hypothesisand theorems. The second group makes it possible to provide scheme consistency with allkinds of elements and synonymy between them. This paper gives the list of ERM-scheme checksand describes theorem sources and their impact on resulting scheme.

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