SYNTACTIC CHARACTERIZATION OF MACHINE PARTS SHAPES

Abstract

In the paper a general purpose parts description language is presented. This language seems to be particularly adequate for the automatic processing of the CAD/CAM system. The description method of machine parts, developed in the paper, is associated not only with individual parts but also with their classes. Each of these classes is created by parts of “similar shapes.” This similarity is determined by the “structure” (configuration) of primitives in contours describing machine parts. This structure is defined in a syntactic manner by means of a formal language generated by the extended context-free grammar (ECFg for short). The right hand sides of the production rules of ECFg are regular expressions over the terminal and non-terminal symbols. It appears quite natural to assume that ECFg generating contours (which uniquely determine machine parts) is in the so-called chain form. ECFGg in the chain form is a modification of the simple chain grammar which has been introduced and investigated by Nijholt in [13]. A very simple (bottom-up) parsing method for ECFg in the chain form is provided. That last grammar may be easily converted into the regular right part grammar (RRPg for short). In the paper a very simple method for constructing of LR(k) paiser for RRPg, generating contours, is given.