Semantic method of database designing and its prospects opening withapplication of the ERM data model

The problem under investigation is database schemas designing. A classical method of relationsdecomposition is one of approaches to the decision of this problem. It is characterized bysuch negative factors, as nonconventional for the majority of people way of perception and formalization,practical inapplicability for complex data domains and ambiguity of the problem decision.Research of a DB designing problem has led to introducing of semantic data models whichprovide high-level formal representation of a data domain. They should remove the first twodrawbacks of a classical method - unnaturalness of representations for the person and inapplicabilityfor complex data domains.But, as commercial DBMS are not going to support directly semantic data models, translationof DB schemas from language of these models to DBMSs language and first of all - relationalone is needed. Practically when the first publications on ER-model were published the basic stepsof a semantic method of relational DB designing began to appear.An application of a semantic method of relational DB designing depends on two factors -apart from knowledge and skills of the person, - expressive means capacity of semantic model inuse and the comprehensive semantic DB schemas analysis in the rules of translation being applied.An ideal application of a semantic method is characterized by the following features.1. At the stage of initial data domain descriptions formalization within the framework of semanticmodel the data scheme should incorporate definitions of all basic concepts and all the lawsof relations between them. The ideal semantic data domain scheme should contain its completeformal description so that all subsequent intermodelling scheme transformations may have onlysyntactic character and consequently the repeated analysis of a data domain semantics and workwith texts in a natural language will not be necessary.2. The rules of scheme transformation used in a method should be so accurate as to take accountof every element of the semantic scheme. Therefore DBMS-oriented scheme proves to beideal from all points of view.The application of semantic data model «Entity - Relationship - Mapping» in combinationwith elaborated rules of scheme translation gives almost ideal semantic method of relational DBdesigning. Its implementation in CASE-tool will reduce the problem of designing to ERMschemeconstruction and application of automatic transformation means.

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