Integrating “Free” Word Order Syntax and Information Structure

Integrating "Free" Word Order Syntax and Information Structure Beryl Hoffman* Dept. of Computer and Information Science University of Pennsylvania (hoffman@linc.cis.upenn.edu) Abstract Multiset-CCG is a combinatory catego- rial formalism that can capture the syn- tax and interpretation of "free" word or- der in languages such as Turkish. The formalism compositionally derives the predicate-argument structure and the in- formation structure (e.g. topic, focus) of a sentence, and uniformly handles word order variation among arguments and adjuncts within a clause, as well as in complex clauses and across clause boundaries. 1 Introduction In this paper, I present a categorial formalism, Multiset CCG (based on Combinatory Categorial Grammars (Steedman, 1985; Steedman, 1991)), that captures the syntax and context-dependent interpretation of "free" word order in languages such as Turkish. Word order variation in rela- tively free word order languages, such as Czech, Finnish, German, Japanese, Korean, Turkish, is used to convey distinctions in meaning that go beyond traditional propositional semantics. The word order in these languages serves to structure the information being conveyed to the hearer, e.g. by indicating what is the topic and the focus of the sentence (as will be defined in the next section). In fixed word order languages such as English, these are indicated largely through intonation and stress rather than word order. The context-appropriate use of "free" word or- der is of considerable importance in developing practical applications in natural language gener- ation, machine translation, and machine-assisted translation. I have implemented a database query system in Prolog, described in (Hoffman, 1994), which uses Multiset CCG to interpret and gen: crate Turkish sentences with context-appropriate word orders. Here, I concentrate on further devel- *I would like to thank Mark Steedman, Ellen Prince, and the support of NSF Grant SBR 8920230. oping the formalism, especially to handle complex sentences. There have been other formalisms that inte- grate information structure into the grammar for "free" word order languages, e.g. (Sgall et al, 1986; Engdahl/Vallduvi, 1994; Steinberger, 1994). However, I believe my approach is the first to tackle complex sentences with embedded infor- mation structures and discontinuous constituents. Multiset CCG can handle free word order among arguments and adjuncts in all clauses, as well as word order variation across clause boundaries, i.e. long distance scrambling. The advantage of using a combinatory categorial formalism is that it provides a compositional and flexible sur- face structure, which allows syntactic constituents to easily correspond with information structure units. A novel characteristic of this approach is that the context-appropriate use of word or- der is captured by compositionally building the predicate-argument structure (AS) and the infor- mation structure (IS) of a sentence in parallel. After presenting the motivating Turkish data in Section 2, I present a competence grammar for Turkish in Section 3 that captures the basic syn- tactic and semantic relationships between predi- cates and their arguments or adjuncts while al- lowing "free" word order. This grammar, which derives the predicate-argument structure is then integrated with the information structure in Sec- tion 4. In Section 5, the …

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