Metalanguage of Normal Forms of Knowledge
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METALANGUAGE OF NORMAL FORMS OF KNOWLEDGE A. F. Kurgaev1† and S. N. Grigoriev1‡
UDC 004.8
Abstract. A metalanguage of normal forms of knowledge and its text and graphic descriptions are presented. Numerous linguistic examples including the syntax of a subset of simple English sentences and a metalanguage of Extended Backus–Naur Form are formally described in text and graphic forms. The conclusion is made that the metalanguage presented can be compared favorably with human capabilities of knowledge representation and use. Keywords: syntax, metalanguage of Normal Forms of Knowledge, graphic tool of a metalanguage, formal description of a metalanguage, Extended Backus–Naur Form, syntax of simple English sentences. INTRODUCTION Man usually perceives only entities that have a form; there is no object without form. Any form is perceived by a person when he realizes its structure on the basis of knowledge of the syntax of the language for describing the set of forms of objects of some class. To strictly and exactly describe syntaxes of languages, special metalanguages (languages for describing languages) are used [1]. The metalinguistic Backus–Naur Form (BNF) and Extended BNF (EBNF) [2] are most widespread. However, as a language for the representation of knowledge, the EBNF metalanguage (and other well-known metalanguages) has definite drawbacks. In particular, the EBNF language created initially for highly specialized problems and supporting their solution rather well is not functionally complete and, hence, it is unsuitable for representing arbitrary knowledge. The objective of this article is the elimination of drawbacks of well-known metalanguages within the framework of a new method of representation and use of knowledge [1, 3] and application of this method to the description of a number of linguistic examples. A NEW METALANGUAGE FOR DESCRIBING KNOWLEDGE With the help of the BNF metalanguage, its extension, or an arbitrary other metalanguage, syntactic structures of an arbitrary object language are specified in the form of a system of rules, i.e., formulas defining relations between terminals and nonterminals. Terminals are elements of a structure that do not have their own structure and consist of identifiers or strings, i.e., sequences of symbols in single or double quotes, which are defined out of BNF descriptions. Nonterminals are elements of a structure that have both proper names and structures. A complete description of a structure is a collection of rules that define all nonterminals in such a way as to provide the reduction of each of them to a combination of terminals with sequential (recursive) application of rules. 1
V. M. Glushkov Institute of Cybernetics, National Academy of Sciences of Ukraine, Kyiv, Ukraine, [email protected]; ‡[email protected]. Translated from Kibernetika i Sistemnyi Analiz, No. 6, November–December, 2016, pp. 11–20. Original article submitted February 23, 2016.
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1060-0396/16/5206-0839 ©2016 Springer Science+Business Media New York
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