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<Paper uid="C90-3073">
  <Title>Knowledge Representation and Semantics in a Complex Domain: The UNIX Natural Language Help System GOETHE</Title>
  <Section position="5" start_page="361" end_page="361" type="concl">
    <SectionTitle>
4 Frame Semantics
</SectionTitle>
    <Paragraph position="0"> Output of the parser in GOETHE is a possibly incorrect, or incomplete, semantic representation where the meaning of tile individual- and predicate-constants of tile logical representation are represented as frame-theoretic icons (Hcyer et.al. :19881).</Paragraph>
    <Paragraph position="1"> We call this kind of semantic representation flame-semantics, or database-semantics (Hausser 1989). Taking the frame representation of UN\[X (including attached procedares and, additionally, the protocolled history) as the context-model relative to which a user's input is interpreted, this flame-semantics allows for a simple and efficient processing of a semantic representation for correction, completion, or the retrieval of the requested information via the knowledge base manager. As an illustration, consider the following examples:  app(descending, attr(date,_))\]\] (Note that &amp;quot;list directory&amp;quot; = &amp;quot;show all files&amp;quot;; &amp;quot;so&amp;quot; = source object, &amp;quot;too&amp;quot; = main object, &amp;quot;attr&amp;quot; = attribute).</Paragraph>
    <Paragraph position="2"> Why: search for a fl'ame representing a program in the history and compare the used commands with the intended goal with respect to identities Why-not: search for a flame representing a program in the history and compare the used commands with the intended goal with respect to differences.</Paragraph>
    <Paragraph position="3"> Literature In these lists (which might equally be represented as trees), each argument points to a frame in the UNIX knowledge base.</Paragraph>
    <Paragraph position="4"> Semantic processing then basically consists of successively unifying each of these frames (where the predicates are slots in the frame referred to by the respective mother-node).</Paragraph>
    <Paragraph position="5"> In case the unification of a set of frames fails, GOETttE tries a number of heuristics to actfieve unification, including: Identificatior,. (identifying the referents of proper names as denoting a file, a directory, a UNIX command, an owner, or a group), generalisation (taking .:he frame-generalisation of the (first) action node as a candidate for unification), and preconditioncheclc (checking whether existence of a file, ownership, and read-, write-, executionrights are fulfilled a:; required).</Paragraph>
    <Paragraph position="6"> Once a set of frames is consistent, retri~:ving the answer to a request is stirred by the frames for How, Why, and Why-not, always appearing on the top-level node of the '~emantic representation. These frames can be understood as representing strategies for searching the knowledge base as follows: ltow: Search for a frame with a goal component containing a special command entry</Paragraph>
  </Section>
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