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<Paper uid="H86-1020">
  <Title>SOME COMPUTATIONAL PROPERTIES OF TREE ADJOINING GRAMMARS*</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1. INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> Investigation of constrained grammatical systems from the point of view of their linguistic adequacy and theiC/ computational tractability has been a major concern of computational linguists for the last several years. Generalized Phrase Structure grammars (GPSG), Lexical Functional grammars&amp;quot; (LFG), Phrase Linking grammars (PLG), and Tree Adjoining grammars (TAG) are some key examples of grammatical systems that have been and still continue to be investigated along these lines.</Paragraph>
    <Paragraph position="1"> Some of the basic notions of TAG% were introduced in \[Joshi, Levy, and Takahashi,1975\] and \[Jo6hi,lQ83\]. Some preliminary investigations of the linguistic relevance and some computational properties were also carried out in \[Jo6hi,1983\]. More recently, a detailed investigation of the linguistic relevance of TAG's were carried out by \[Kroch and Joshi,1985\].</Paragraph>
    <Paragraph position="2"> In this paper, we will describe some new results for TAG's, especially in the following areas: (1) parsing complexity of TAG's, (2) some closure results for TAG's, and (3) the relationship to Head grammars. These topics will be covered in Sections 3, 4, and S respectively. In section 2, we will give an introduction to TAG's. In section 6, we will state some properties not discussed here. A detailed exposition of these results is given in \[Vijay-Shankar and Joshi,1985\]. &amp;quot;This work wu partially supported by NSF Grants MCS-821011e-CER. MCS-82~7204. We want to thuk Carl P'oUard, Kelly Roach, David SeaM, tad David Weir. We have benefited enormously by valuable dbcussion8 with them.</Paragraph>
  </Section>
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