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<p>Each retrieval strategy incorporates a specific model for its document representation purposes. The picture on the right illustrates the relationship of some common models. In the picture, the models are categorized according to two dimensions: the mathematical basis and the properties of the model.</p>

<p><big> First dimension: mathematical basis </big></p>
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* Set-theoretic models represent documents as <a href="page.php?w=Set_%28mathematics%29">set</a>s of words or phrases. Similarities are usually derived from set-theoretic operations on those</p><p>
<a accesskey="1" href="page.php?w=information_retrieval&amp;p=21">1.Previous</a><br />
<a accesskey="3" href="page.php?w=information_retrieval&amp;p=23">3.Next</a>
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