Functional Structures for Parsing Dependency Constraints

In the theory of computation a new viewpoint is digging in: to compute is to pin down the constraints that hold in a given problem domain, and a goal for computation. It is up to an interpreter to perform search for the goal in the problem domain. The result of computation follows then indirectly from the search process. Strongly pronounced and in wide use this vantage point becomes in Prolog. Recently fresh views of parsing as constraint systems have also surfaced, such as FUG (Kay, 1985; Karttunen and Kay, 1985), LFG (Bresnan, 1978), and PATR-II (Schieber, 1985). In these languages, a user writes only grammatical constraints and need not import control instructions. The interpreter searches for a grammatical configuration that "explains" a given input sentence without violating the constraints. These new grammars advocate yet another, more abstract departure from procedural description. Grammars for parsing have predominantly used generative rewrite rules. The ideological underpinning of parsing has been in the past that of the emulation of generative tllstories of configurations. The new formalisms express grammars as functional structures. We have defined a language DPL (Dependency Parsing Language) to meet the needs of parsing a highly inflectional, agglutinating language (Nelimarkka et al., 1984). The language enforces dependency approach which accords better than phrase structure rules with the needs of non-configurational languages. DPL language and its compiler constitutes .just one component of a language-based environment we have implemented for the development of parsers (Lehtota et al., 1985). In DPL, a grammar is comprised of functions, relations, and automata. The automata, which control the parsing process, have compelled a person who writes grammar to heed control unwanted extent. This paper describes a high-level language FUNDPL (FUNctional DPL) we have designed on top of DPL. In FUNDPL, a grammar is built out of functions, relations, and functional structures. FUNDPL is a constraint system which liberates a grammar writer from control anxieties.