Sentence Fragments Regular Structures

SENTENCE FRAGMENTS REGULAR STRUCTURES Marcia C. Linebarger, Deborah A. Dahl, Lynette Hirschman, Rebecca J. Passonneau Paoli Research Center Unlsys Corporation P.O. Box 517 Paoli, PA ABSTRACT This paper describes an analysis of telegraphic fragments as regular structures (not errors) han- dled by rn~n~nal extensions to a system designed for processing the standard language. The modu- lar approach which has been implemented in the Unlsys natural language processing system PUNDIT is based on a division of labor in which syntax regulates the occurrence and distribution of elided elements, and semantics and pragumtics use the system's standard mechankms to inter- pret them. 1. INTRODUCTION In t]~ paper we discuss the syntactic, semantic, and pragmatic analysis of fragmentary sentences in English. Our central claim is that these sentences, which have often been classified in the literature with truly erroneous input such as misspellings (see, for example, the work dis- cussed in ~wnsny1980, Thompson1980, Kwnsny1981, Sondheimer1983, Eustman1981, Jen- sen1983]), are regular structures which can be processed by adding a small number of rules to the grammar and other components of the sys- tem. The syntactic regularity of fragment struc- tures has been demonstrated elsewhere, notably in ~/larsh1983, Hirschman1983]; we will focus here upon the regularity of these structures across all levels of linguistic representation. Because the syntactic component regularizes these structures into a form almost indistinguishable from full tThis work has been supported in part by DARPA under contract N00014-85-C-0012, administered by the Office of Naval Research; by National Science Foundation contract DCR-85-02205; and by Independent R~D fuudinz from Sys- tens Development Corporation, now part of Unisys Corpora- tion. Approved for public release, distribution unlimited. assertions, the semantic and pragmatic com- ponents are able to interpret them with few or no extensions to existing mechanisms. This process of incremental regularisation of fragment struc- tures~is possible only within a linguistically modu- lar system. Furthermore, we claim that although fra~nents may occur more frequently in special- ised sublanguages than in the standard grammar, they do not provide evidence that sublanguages are based on gra,~m*tical principles fundamen- tally different from those underlying standard languages, as claimed by ~itspatrick1986], for example. This paper is divided into five sections. The introductory section defines fragments and describes the scope of our work. In the second section, we consider certain properties of sentence fragments which motivate a modular approach. The third section describes our implementation of processing for fragments, to which each com- ponent of the system makes a distinct contribu- tion. The fourth section describes the temporal analysis of fragments. Finally, the fifth section discusses the status of sublanguages characterized by these telegraphic constructions. We define fragments as regular structures which are distinguished from full assertions by a missing element or elements which are normally syntactically obligatory. We distinguish them from errors on the basis of their regularity and consistency of interpretation, and because they appear to be generated intentionally. We are not denying the existence of true errors, nor that pro- ceasing sentences containing true errors may require sophisticated …

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