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<Paper uid="P95-1008">
  <Title>DATR Theories and DATR Models</Title>
  <Section position="6" start_page="59" end_page="59" type="concl">
    <SectionTitle>
5 Conclusions
</SectionTitle>
    <Paragraph position="0"> The work described in this paper fulfils one of the objectives of the DATR programme: to provide the language with an explicit, declarative semantics. We have presented a formal model of DATR as a language for defining partial functions and this model has been contrasted with an informal view of DATR as a language for representing inheritance hierarchies. The approach provides a transparent treatment of DATR's notion of (local and global) context and accounts for DATR's default mechanism by regarding value descriptors (semantically) as families of values indexed by paths.</Paragraph>
    <Paragraph position="1"> The provision of a formal semantics for DATR is important for several reasons. First, it provides the DATR user with a concise, implementationindependent account of the meaning of DATR theories. Second, it serves as a standard against which other, operational definitions of the formalism can be judged. Indeed, in the absence of such a standard, it is impossible to demonstrate formally the correctness of novel implementation strategies (for an example of such a strategy, see (Langer, 1994)).</Paragraph>
    <Paragraph position="2"> Third, the process of formalisation itself aids our understanding of the language and its relationship to other non-monotonic, attribute-value formalisms.</Paragraph>
    <Paragraph position="3"> Finally, the semantics presented in this paper provides a sound basis for subsequent investigations into the mathematical and computational properties of DATR.</Paragraph>
  </Section>
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