An Approach to the Construction of a Level Description of Classes by Means of a Predicate Calculus Language

A problem of construction of a level description of classes with objects characterized by properties of their elements and relations between them is under consi\-de\-ration in the paper. The problems of recognition and analysis of such objects are NP-hard, but if descriptions of classes contain short enough and frequently occurred sub-formulas then it is possible to build a level description of classes essentially decreasing an exponent in upper bounds of steps for an algorithm solving the problemr. Usually an extracting of these sub-formulas is leaved to the investigator will. An approach to their automatic extraction is proposed in the paper.