Preference logic grammars

Preference logic grammars (PLGs) are introduced in this paper as a concise, declarative, modular, and efficient means of resolving ambiguity in logic grammars. Preference logic grammars can be thought as extensions of definit e clause grammars (DCGs) and definite-clause translation grammars (DCTGs). Just as DCGs and DCTGs can be directly translated into logic programs, PLGs can be translated into preference logic programs (PLPs), which we introduc ed in our earlier work. We discuss two applications of PLGs: optimal parsin g, and ambiguity resolution in programming-language and natural-language gr ammars. Optimal parsing is an extension of parsing wherein costs are associ ated with the different (ambiguous) parses of a string and the preferred pa rse is the one with least cost. Many problems can be viewed as optimal pars ing problems, e.g., code generation, document layout, etc. In the area of n atural language parsing, we illustrate the use of preference clauses for re solution of prepositional phrase attachment ambiguities, and point out the growing consensus in the literature on the need to explicitly specify prefe rence criteria for ambiguity resolution. (C) 1999 Elsevier Science Ltd. All rights reserved.