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<Paper uid="C86-1050">
  <Title>A Simple Reconstruction of GPSG</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction I
</SectionTitle>
    <Paragraph position="0"> Like most llngafistic theories, the theory of generalized phrase structure grammar (GPSG) has described language axiomatically, that is, as a set of universal and language-specific constraints on the we\[l-formedncss of linguistic elements of some sort. In the case of GPSG, these elements are trees whose nodes are themselves structured entltics from a domain of categories (a type of feature ~trueture \[6\]). The proposed axioms have become quite complex, culminating in the ambitious recent volume by Gazdar, Klein, Pullum, and Sag entitled Generalized Phrase Structure Grammar \[2\]. The coverage and detailed analysis of English grammar in this work are impressive, in part because of the complexity of the axiomatic system developed by the author.</Paragraph>
    <Paragraph position="1"> In this paper, we examine the possibility that simpler descriptions of the same theory can be achieved through a slightly different, albeit still axiomatic, method. Rather than characterize the well-formed trees driectly, we progress in two stages by procedurally characterizing tim well-formedaess axioms themselves, which in turn charaetei'ize the trees. In particular, we give a procedure which converts GPSG gramma~ into gramma~ written lThls research was m~de possible by a gift. from the System Development Foundation.</Paragraph>
    <Paragraph position="2"> I am indebted to Lauri K~rttuncn and Ray Perrault for their eomrael~te on earlier drafts, and to Roger Evans, Gerald Gszdsr~ Ivan S~.$t ltenry Thompson, and members of the Foundations of Grammar project at the Center for the Study of Language and Information for their helpful discussions during the development of this work.</Paragraph>
    <Paragraph position="3"> in a unification-b~qed formalism, the PATR-II formalism developed at SRI International (henceforth PATR) \[5\], which h~s its own declarative semmltics, and which can therefore be viewed &amp;s an axiomatization of string well-formedness constraints. 2 The characterization of GPSG thus obtained is simpler and better defined than the version described by Gazdar et al. The semantics of the formalism is given directly through the reduction to PATR. Also, the PATR axiomatization has a clear construetire interpretation, unlike that used in Gazdar et al., thus making the system more amenable to computational implementation.</Paragraph>
    <Paragraph position="4"> Finally, the characteristics of the coml~ilation--the difficulty or ease with which the various devices can be encoded in PATR-can provide a measure of the expressiveness and indispensability of these devices in GPSG.</Paragraph>
  </Section>
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