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<Paper uid="W97-0613">
  <Title>The &amp;quot;Casual Cashmere Diaper Bag&amp;quot;: Constraining Speech Recognition Using Examples</Title>
  <Section position="5" start_page="63" end_page="63" type="metho">
    <SectionTitle>
4 Logic versus reality
</SectionTitle>
    <Paragraph position="0"/>
    <Section position="1" start_page="63" end_page="63" type="sub_section">
      <SectionTitle>
4.1 A mysterious deafness
</SectionTitle>
      <Paragraph position="0"> One final problem must be addressed to make this scheme actually useful; there are sure to be some &amp;quot;reasonable&amp;quot; combinations of modifiers and basic items that the catalog makers just do not include in their catalog. If there were &amp;quot;canvas jackets&amp;quot; and &amp;quot;denim jeans&amp;quot; in the catalog but no &amp;quot;denim jackets,&amp;quot; then unless jeans and jackets shared a common &amp;quot;kind of thing&amp;quot; property on which to base the grammar restrictions, the restricted grammar could not hear the phrase &amp;quot;denim jacket&amp;quot;. Presented with those sounds, it would probably produce something like the &amp;quot;d'women jacket&amp;quot; pronunciation of &amp;quot;the women\['s\] jacket&amp;quot;, but it could not &amp;quot;hear&amp;quot; what the user actually said. This would be baffling to a naive user of the system, especially since rephrasing his request to include % jacket made of denim&amp;quot; would also fail.</Paragraph>
    </Section>
    <Section position="2" start_page="63" end_page="63" type="sub_section">
      <SectionTitle>
4.2 Filling in the gaps
</SectionTitle>
      <Paragraph position="0"> To fix this shortcoming, the examples that generate the automatic marking of the lexicon must be augmented to include the logical extensions of the actual database of &amp;quot;real&amp;quot; items. When proposing this approach, Nicole Yankelovich loosely described it as &amp;quot;listing all the things that aren't in the catalog&amp;quot;. Of course, taking this literally would be an unbounded task and would defeat the whole goal of restricting the grammar; such a list would include the infamous cashmere diaper bag! What we really needed was a listing of the things that one might logically expect to find but which do not exist in this particular catalog. In our Lands' End example, we created pages of &amp;quot;missing&amp;quot; items and associated these explicitly missing pages as phantom pages under their logical parent pages in the catalog. These phantom pages serve to attach the information we give the customer when we report the omission. With this addition to the scheme, the user can be &amp;quot;heard&amp;quot; asking for a denim jacket, and will be told something helpful in 3 response</Paragraph>
    </Section>
  </Section>
  <Section position="6" start_page="63" end_page="64" type="metho">
    <SectionTitle>
5 System Details
</SectionTitle>
    <Paragraph position="0"> The restrictions computed by this scheme must be applied to the speech recognizer if any reduction in perplexity is to be achieved. Testing restrictions during SR or selecting &amp;quot;semantically&amp;quot; among the n-best are both possible implementations. Neither works with currently available SRs; these SRs use BNF garmmars and do not deliver semantically distinct alternatives for n-best (Hemphill, 1993; Smith and Bates, 1993).</Paragraph>
    <Section position="1" start_page="63" end_page="63" type="sub_section">
      <SectionTitle>
5.1 Compiling restrictions in the SR
</SectionTitle>
      <Paragraph position="0"> grammar The tool we use to impose these restrictions is a compiler capable of converting a grammar composed of patterns and calculated &amp;quot;semantic&amp;quot; restrictions into two compiled grammars: one for use in a speech recognizer and one to parse the recognized words and produce a structure representing the relevant semantics of the sentence. The Unified Grammar and its associated tools fill this requirement, providing a generally adequate approximation to this ideal compiler. The ideal compiler would turn the patterns and restrictions into just patterns, and do so without expanding the compact notation of the original grammar into some &amp;quot;rolled-out&amp;quot; form that is too large for the SR to use; this compactness requirement rules out any approach which ennumerates the acceptable sentences of the grammar. The Unified Grammar compiler produces a patterns-only grammar that also reflects the restrictions by precomputing these tests, when possible, to create more specific patterns reflecting the constraints. It omits restrictions that are too complex for it to effect, thus allowing all the good utterances and possibly some bad ones as well.</Paragraph>
    </Section>
    <Section position="2" start_page="63" end_page="64" type="sub_section">
      <SectionTitle>
5.2 Proeesing steps
</SectionTitle>
      <Paragraph position="0"> To implement the example-based restrictions, the Unified Grammar language was extended to include aWe attach explicit helpful messages to some phantom pages (&amp;quot;Sorry, but the jackets do not come in denim, only Polartec, Thinsulate, and wool&amp;quot;) and otherwise generate a message indicating the query was heard, but no such item is in this catalog.</Paragraph>
      <Paragraph position="1">  tests that could be disabled or enabled with a global switch, and then the following processing was used:  1. Disable the feature restrictions and compile the Unified Grammar to produce a semantic grammar. null 2. Parse the (written) page descriptors with the  &amp;quot;relaxed&amp;quot; semantic parser, building an index of all the parses which can be used later to locate the related pages of the catalog.</Paragraph>
      <Paragraph position="2"> 3. Reprocess this index to extract the information about existing modifier types and use this information to add the implied markings to the lexicon.</Paragraph>
      <Paragraph position="3"> 4. Turn the global switch to enable the lexical restrictions and compile the Unified Grammar again to produce the speech recognition grammar. The compiler will use the enhanced lexicon while applying the restrictions now enabled, and this will produce a &amp;quot;tight&amp;quot; speech recognition grammar.</Paragraph>
      <Paragraph position="4"> 5. Use the restricted grammars for both speech recognition and semantics extraction when running the catalog with users, so that the system can &amp;quot;hear&amp;quot; and process &amp;quot;canvas diaper bag&amp;quot; but not &amp;quot;cashmere diaper bag&amp;quot;.</Paragraph>
    </Section>
  </Section>
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