Nominalizations in PUNDIT

NOMINALIZATIONS IN PUNDIT Deborah A. Dahl, Martha S. Palmer, Rebecca J. Passonneau Paoli Research Center UNISYS Defense Systems 1 Defense Systems, UNISYS P.O Box 517 Paoli, PA 19301 USA ABSTRACT This paper describes the treatment of nomi- nalizations in the PUNDIT text processing system. A single semantic definition is used for both nomi- nalizations and the verbs to which they are related, with the same semantic roles, decomposi- tions, and selectional restrictions on the semantic roles. However, because syntactically nominaliza- tions are noun phrases, the processing which pro- duces the semantic representation is different in several respects from that used for clauses. (1) The rules relating the syntactic positions of the constituents to the roles that they can fill are different. (2) The fact that nominailzations are untensed while clauses normally are tensed means that an alternative treatment of time is required for nomlnalizations. (3) Because none of the argu- ments of a nominallzation is syntactically obllga- tory, some differences in the control of the filling of roles are required, in particular, roles can be filled as part of reference resolution for the nomi- nalization. The differences in processing are cap- tured by allowing the semantic interpreter to operate in two different modes, one for clauses, and one for nominalizations. Because many noml- nalizations are noun-noun compounds, this approach also addresses this problem, by suggest- ing a way of dealing with one relatively tractable subset of noun-noun compounds. 1Formerly SDC-A Burroughs Company. 1. Introduction In this paper we will discuss the analysis of nominalizations in the PUNDIT text processing system. 2 Syntactically, nomlnalizations are noun phrases, as in examples (I)-(7). (1) An inspection of lube oil filter revealed metal particles. (2) Lou of lube oll preuure occurred during operation. (3) SAC received hifh ueafe. (4) In~eeti#ation revealed adequate lube oil. (5) Request replacement of SAC.. (6) Erosion of impellor blade tip is evident. (7) Unit has low output air pressure, resulting in ale*# gae turbine atarte. Semantically, however, nominaliTatlons resemble clauses, with a predlcate/argument structure like that of the related verb. Our treatment attempts to capture these resemblances in such a way that very little machinery is needed to analyze nomi- nalizations other than that already in place for other noun phrases and clauses. There are two types of differences between the treatment of nomlnalizatlons and that of clauses. There are those based on linqui~tle differences, related to (1) the mapping between syntactic arguments and semantic roles, which is I The research described in this paper was supported in part by DARPA under contract N000014-85-C-0012, admin- istered by the Office of Naval Research. APPROVED FOR 131 different in nomlnalisations and clauses, and (2) tense, which nomlnallsations lack. There are also differences in control; in particular, control of the filling of semantic roles and control of reference resolution. All of these issues will be discussed in detail below. 2. Clause analysis The semantic processing to be described in this paper is part of the PUNDIT s system for processing natural language …

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