How difficult would it be to implement something like Cover Density
ranking for Lucene? Has anyone tried it?
Cover density is described at http://citeseer.ist.psu.edu/558750.html , and is supposed to be particularly good for short queries of the type that you get in many web applications.
I just glanced at the paper, so my analysis may be wrong, but I think one could implement cover density ranking in Lucene with spans (only in CVS, not in 1.3). I think spans correspond to covers in this paper. But you'd need to alter SpanScorer.java to implement the cover scoring described in that paper. And you'd probably need to use a custom Similarity implementation, which disables most other scoring (tf=1.0, idf=1.0, etc.), but exaggerates coordination. Finally, you'd need to construct span queries. Or something like that.
If someone tries this, please tell us how it works.
Doug
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