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<Paper uid="J79-1053">
  <Title>TABLE OF CON'I'ENrl'S</Title>
  <Section position="18" start_page="78" end_page="78" type="concl">
    <SectionTitle>
TENSION
</SectionTitle>
    <Paragraph position="0"> Units of the measurement. e.g., FT.</Paragraph>
    <Paragraph position="1"> Numeric or symbolic espression which is the calculated value of a variable.</Paragraph>
    <Paragraph position="2"> Appendix C: Generated Structures for a Sample Problem This appendix contains snapshots of some of the major data structures produced by ISAAC at various stages in the processing of the sample problem (P8). The first part of the listing shows the st?uctures produced by the parsing and semantic processing of each sentence. After each sentence, the result of the parsing is shown; &lt; S&gt; indicates that a major clause was parsed, and the list of tokens which follows gives the root of the parse tree (the verb) for each of the major clauses which was parsed. This is followed by a listing of each of the tokens produced during parsing. The dump follows all of the semantic processing: the tokens are not used thereafter except in finding pronoun referents.</Paragraph>
    <Paragraph position="3"> Following the dump of the parse structures is a listing of the internal model of the problem as it exists just after all of the input sentences have been processed, but before frame creation and all the subsequent processing. Each of the GENSYM atoms is a separate object in the model. The four atoms UNKNOWNS, DESUNKS, SYSREPLY, and SYSUNITS are global variables whose bindings are the list of all unknowns, the list of desired unknow~~s, the reply to be generated once the problem is solved, and the measurement units used for various types of measurements, respectively.</Paragraph>
    <Paragraph position="4"> The next part of the dump- shows each of the equations presented to SOLVEQ for solution, followed by the answer generated by PRTVAR. The equation (EQUALS 0 0) is caused by a deficiency in CFSURFACE (complete frame for SURFACE) which went unnoticed because it didn't cause any problems. CFSURFACE requires that the force exerted by a surface be perpendicular to the surface; this is fine for an attachment of type CONTACT, but not for one of type PINJOINT, such as the attachment between the rope and the wall. Thus, one of the zeros should be a variable representing the vertical force exerted by the wall. The other zero, representing the vertical force exerted by the rope on the wall, is correct.</Paragraph>
    <Paragraph position="5"> The final part of tlle dump shows the model of the problem at the end of the problem solving and picture generation processes. It can be seen that a great deal of information has been added to the model beyond that which was available immediately after the problem statement was read. The meaning of the information associated with each of the objects in the model is explained in Appendix B.</Paragraph>
  </Section>
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