The connection with term clustering was already made earlier on in the chapter. The spanning tree can be looked upon as a classification of the index terms. One of the important consequences of the model described in this chapter is that it lays down precisely how the tree should be used in retrieval. Earlier work in this area was rather ad hoc and did not lead to conclusive results[40].

It should be clear now that the quantitative model embodies within one theory such diverse topics as term clustering, early association analysis, document frequency weighting, and relevance weighting.

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