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<Paper uid="P97-1050">
  <Title>Efficient Construction of Underspecified Semantics under Massive Ambiguity</Title>
  <Section position="7" start_page="391" end_page="392" type="evalu">
    <SectionTitle>
5 Implementation and Experimental
</SectionTitle>
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    <Section position="1" start_page="391" end_page="392" type="sub_section">
      <SectionTitle>
Results
</SectionTitle>
      <Paragraph position="0"> The algorithm has been implemented for the PROLOG (or DCG) constraint system, i.e., constraints are equations over first-order terms. Two implementations have been done. One in the concurrent constraint language OZ (SmolkaTreinen 96) and one in Sicstus Prolog. 9 The following results relate to the Prolog implementation, ldeg Fig. 5 shows the resulting packed UDRS for the example forest in Fig. 2. Fig. 6 displays the SEM part as a graph. The disjunctive binding environment only encodes what the variable referents B and D (in conjunction with the corresponding labels A and C) may be bound to to: one of el, x2, or x3 (and likewise the corresponding label). Executing the goal deny (509,1, \[B, A, D, C\] ) yields the five solutions: A = ii, B = el, C = ii, D = el ? ; A = 12, B = x2, C = ii, D = el ? ; A = 11, B = el, C = 14, D = x3 ? ; A = 12, B = x2. C = 12, D = x2 ? ; A = 12, B = x2, C = 14, D = x3 ? ; no I  ?-Table 1 gives execution times used for semantics construction of sentences of the form I saw a man (on a hill) n for different n. The machine used for degThe OZ implementation has the advantage that feature structure constraint solving is built-in. Our implementation actually represents the DCG terms as a feature structures. Unfortunately it is an order of magnitude slower than the Prolog version. The reason for this presumably lies in the fact that meta-logical operations the algorithm needs, like generalise and copy_term have been modeled in OZ and not on the logical level were they properly belong, namely the constraint solver.</Paragraph>
      <Paragraph position="2"> the experiment was a Sun Ultra-2 (168MHz), running Sicstus 3.0~3. In a further experiment an n-ary anti_unify operation was implemented, which improved execution times for the larger sentences, e.g., the 16 PP sentence took 750 msec. These results approximately fit the expectations from the theoretical complexity bound.</Paragraph>
    </Section>
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