Morphology-Syntax Interface for Turkish LFG

Proceedings of the 21st International Conference on Computational Linguistics and 44th Annual Meeting of the ACL, pages 153–160, Sydney, July 2006. c⃝2006 Association for Computational Linguistics Morphology-Syntax Interface for Turkish LFG ¨Ozlem C¸ etino˘glu Faculty of Engineering and Natural Sciences Sabancı University 34956, Istanbul, Turkey ozlemc@su.sabanciuniv.edu Kemal Oflazer Faculty of Engineering and Natural Sciences Sabancı University 34956, Istanbul, Turkey oflazer@sabanciuniv.edu Abstract This paper investigates the use of sublexi- cal units as a solution to handling the com- plex morphology with productive deriva- tional processes, in the development of a lexical functional grammar for Turkish. Such sublexical units make it possible to expose the internal structure of words with multiple derivations to the grammar rules in a uniform manner. This in turn leads to more succinct and manageable rules. Fur- ther, the semantics of the derivations can also be systematically reflected in a com- positional way by constructing PRED val- ues on the fly. We illustrate how we use sublexical units for handling simple pro- ductive derivational morphology and more interesting cases such as causativization, etc., which change verb valency. Our pri- ority is to handle several linguistic phe- nomena in order to observe the effects of our approach on both the c-structure and the f-structure representation, and gram- mar writing, leaving the coverage and evaluation issues aside for the moment. 1 Introduction This paper presents highlights of a large scale lex- ical functional grammar for Turkish that is being developed in the context of the ParGram project1 In order to incorporate in a manageable way, the complex morphology and the syntactic relations mediated by morphological units, and to handle lexical representations of very productive deriva- tions, we have opted to develop the grammar using sublexical units called inflectional groups. Inflectional groups (IGs hereafter) represent the inflectional properties of segments of a complex 1http://www2.parc.com/istl/groups/nltt/ pargram/ word structure separated by derivational bound- aries. An IG is typically larger than a morpheme but smaller than a word (except when the word has no derivational morphology in which case the IG corresponds to the word). It turns out that it is the IGs that actually define syntactic relations be- tween words. A grammar for Turkish that is based on words as units would have to refer to informa- tion encoded at arbitrary positions in words, mak- ing the task of the grammar writer much harder. On the other hand, treating morphemes as units in the grammar level implies that the grammar will have to know about morphotactics making either the morphological analyzer redundant, or repeat- ing the information in the morphological analyzer at the grammar level which is not very desirable. IGs bring a certain form of normalization to the lexical representation of a language like Turkish, so that units in which the grammar rules refer to are simple enough to allow easy access to the in- formation encoded in complex word structures. That IGs delineate productive derivational pro- cesses in words necessitates a mechanism that re- flects the effect of the derivations to …

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