Finite-State Phonology in HPSG

FINITE-STATE PHONOLOGY IN HPSG Steven Bird University of Edinburgh, Centre for Cognitive Science 2 Buccleuch Place, Edinburgh EH8 9LW, Scotland Emaih Steven. Bird@edinburgh. ac. uk ABSTRACT Attention on constraint-based grammar formalisms such as Head-driven Phrase Structure Grammar (HPS6) has focussed on syntax and semantics to the exclu- sion of phonology. This paper investigates the in- corporation of a non-procedural theory of phonology into rmSG, based on the 'one-level' model of Bird & Ellison (1992). The standard rule-representation distinction is replaced by the description-object dis- tinction which is more germane in the context of constraint-based grammar. Prosodic domains, which limit the applicability of phonological constraints, are expressed in a prosodic type hierarchy modelled on lfPSG'S lexical type hierarchy. Interactions between phonology and morphology and between phonology and syntax are discussed and exemplified I . 1 Introduction The exclusion of phonology from Head-driven Phrase Structure Grammar (Pollard & Sag, 1987) and re- lated grammar frameworks belonging to the Mon- tague tradition (Dowty et al., 1981; Shieber, 1986) is no doubt due to the perception that much cur- rent theorising in phonology is excessively procedu- ral in nature. While there is an element of truth in this, it is also true that the predilection of constraint- based grammarians for a string-based phonology has predisposed them towards segmental phonology, in which procedural thinking is at its peak. Other vari- eties of phonology--most notably non-linear phonol- ogy (Goldsmith, 1976, et seq.)--have now largely abandoned complex derivational accounts of phono- logical well-formedness in favour of systems of gen- eralised constraints. A defining property of con- straints is that they are not applied in any particular order. Rice (1989, 331) writes that "a general goal IThis research is funded by the U.K. Science and Engineer- ing Research Council, under grant GR/G-22084 Computational Phonology: A Constraim-Based Approach. I am grateful to Mark Ellison, Ewan Klein and Bob Ladd for discussions relating to this work. in recent phonological work has been the elimination of structure-changing processes from the grammar." With structure-changing process gone, all that con- straints do is specify what it means for surface forms to be well-formed 2. A consequence of this paradigm shift in phonology is that the main barrier to the incor- poration of phonology into constraint-based grammar frameworks has now disappeared. In trying to assess the consequences of this pro- gramme for phonology itself, it would be instructive to identify four major ideas or principles that have characterised work in the Montague tradition, out of which constraint-based grammar formalisms have grown. The first is THE PRINCIPLE OF COMPOSITION- ALITY, which requires that the form and interpretation of an expression be a function of the form and inter- pretation of its parts. This principle motivated Bach's well-known RULE-TO-RULE HYPOTItESIS, requiring that the linguistic modules (such as syntax, seman- tics and phonology) be organised in parallel rather than in series, where the output of one module is the input of the next. The second principle is Partee's (1979, 276) WELL-FORMEDNESS CONSTRAINT, which states that well-formed expressions …

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