section follows the discussion
in section 6.5 &#8220;Theories, Models and the World&#8221; of the book <span
 style="font-style: italic;">Knowledge
Representation</span> by John Sowa. From each theory in the lattice of
theories, the partial ordering defines paths to the more generalized
theories above and the more specialized theories below. Figure 4 shows
four ways for moving along paths from one theory to another:
contraction, expansion, revision and analogy.<br>
</p>
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  <li>
    <p><span style="font-