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computing the intermediate dissimilarity coefficient,will need to make a choice of cluster representative ab initio
...Cluster based retrieval Cluster based retrieval has as its foundation the cluster hypothesis,which states that closely associated documents tend to be relevant to the same requests
...Suppose we have a hierarchic classification of documents then a simple search strategy goes as follows refer to Figure 5
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that a search strategy will infallibly find the class of documents containing the relevant documents
...Note that the Cluster Hypothesis refers to given document descriptions
...As can be seen from the above,the Cluster Hypothesis is a convenient way of expressing the aim of such operations as document clustering
...The use of clustering in information retrieval There are a number of discussions in print now which cover the use of clustering in IR
...In choosing a cluster method for use in experimental IR,two,often conflicting,criteria have frequently been used
...1 the method produces a clustering which is unlikely to be altered drastically when further objects are incorporated,i
...2 the method is stable in the sense that small errors in the description of the objects lead to small changes in the clustering;3 the method is independent of the initial ordering of the objects
...These conditions have been adapted from Jardine and Sibson [2]... |
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The appropriateness of stratified hierarchic cluster methods There are many other hierarchic cluster methods,to name but a few:complete link,average link,etc
...Stratified systems of clusters are appropriate because the level of a cluster can be used in retrieval strategies as a parameter analogous to rank position or matching function threshold in a linear search
...Given that hierarchic methods are appropriate for document clustering the question arises:Which method?The answer is that under certain conditions made precise in Jardine and Sibson [2]the only acceptable stratified hierarchic cluster method is single link
...See introduction for definition
...Single link and the minimum spanning tree The single link tree such as the one shown in Figure 3
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