tailieunhanh - Báo cáo khoa học: "MODULAR LOGIC GRAMMARS"

This grammar formalism, a high degree of modularity between syntax and semantics. There is a syntax rule compiler (compiling into Prolog) which takes care of the building of analysis structures and the interface to a clearly separated semantic interpretation component dealing with scoping and the construction of logical forms. The whole system can work in either a one-pass mode or a two-pass mode. [n the one-pass mode, logical forms are built directly during parsing through interleaved calls to semantics, added automatically by the rule compiler. . | MODULAR LOGIC GRAMMARS Michael c. McCord IBM Thomas J. Watson Research Center p. o. Box 218 Yorktown Heights NY 10598 ABSTRACT This report describes a logic grammar formalism Modular Logic Grammars exhibiting a high degree of modularity between syntax and semantics. There is a syntax rule compiler compiling into Prolog which takes care of the building of analysis structures and the interface to a clearly separated semantic interpretation component dealing with scoping and the construction of logical forms. The whole system can work in either a one-pass mode or a two-pass mode. In the one-pass mode logical forms are built directly during parsing through interleaved calls to semantics added automatically by the rule compiler. In the two-pass mode syntactic analysis trees are built automatically in the first pass and then given to the one-pass semantic component. The grammar formalism includes two devices which cause the automatically built syntactic structures to differ from derivation trees in two ways 1 There is a shift operator for dealing with left-embedding constructions such as English possessive noun phrases while using right-recursive rules which are appropriate for Prolog parsing . 2 There is a distinction in the syntactic formalism between strong non-terminals and weak non-terminals which is important for distinguishing major levels of grammar. 1. INTRODUCTION The term logic grammar will be used here in the context of natural language processing to mean a logic programming system implemented normally in Prolog which associates semantic representations normally in some version of predicate logic with natural language text. Logic grammars may have varying degrees on modularity in their treatments of syntax and semantics. There may or may not be an isolatable syntactic component. In writing metamorphosis grammars Colmerauer 1973 or definite clause grammars DCG s a special case of metamorphosis grammars Pereira and Warren. 1980 it is possible to build logical .