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<Paper uid="P80-1003">
  <Title>ON THE EXISTENCE OF PRIMITIVE MEANING UNITS</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
ABSTRACT
</SectionTitle>
    <Paragraph position="0"> Knowledge representation schemes are either based on a set of primitives or not. The decision of whether or not to have a primitive-based scheme is crucial since it affects the knowledge that is stored and how that knowledge may be processed. We suggest that a knowledge representation scheme may not initially have primitives, but may evolve into a prlmltive-based scheme by inferring a set of primitive meaning units based on previous experience. We describe a program that infers its own primitive set and discuss how the inferred primitives may affect the organization of existing information and the subsequent incorporation of new information.</Paragraph>
    <Paragraph position="1"> i. DECIDING HOW TO REPRESENT KNOWLEDGE A crucial decision in the design of a knowledge representation is whether to base it on primitives. A primitive-based scheme postulates a pre-defined set of meaning structures, combination rules and procedures. The primitives may combine according to the rules into more complex representational structures, the procedures interpret what those structures mean. A primltive-free scheme, on the other hand, does not build complex structures from standard building blocks; instead, information is gathered from any available source, such as input and information in previously built meaning structures.</Paragraph>
    <Paragraph position="2"> A hybrid approach postulates a small set of pro-defined meaning units that may be used if applicable and convenient, but is not limited to those units. Such a representation scheme is not truly prlmitive-based since the word &amp;quot;primitive&amp;quot; implies a complete set of pre-deflned meaning units that are the onl 7 ones available for construction. However, we will call this hybrid approach a primitive-based scheme, since it does postulate some pro-defined meaning units that are used in the same manner as primitives.</Paragraph>
  </Section>
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