Lucene-MLM

A mixture of language models ranker for Lucene

Lucene-MLM is a tiny Java library enabling a mixture of language models [1] as a ranker for Lucene 4.

[1] P. Ogilvie, J. Callan. Combining Document Representations for Known-Item Search. SIGIR'03 (2003).

Current Version

0.2.2

Features

The library is built atop the Lucene 4 API (FunctionQuery, ValueSource classes)
Correct computation of Dirichlet priors for terms*

*) the standard implementation of LMSimilarity wrongly retrieves only documents containing all the query terms and assumes non-matched terms as of zero priors

Known Issues

Slower speed performance than that of standard rankers, due to matching against all the query terms (OR semantics). There is a need of top-k pre-ranking for better performance.

Prerequisites

Java 1.6+
Scala 2.9.2+ (optional, used only for tests)
Tested on Lucene 4.8