Combination Approaches in Information Retrieval: Words vs. N-grams and Query Translation vs. Document Translation

This paper reports our proposal and experimental results at the NTCIR-4 CLIR task. For monolingual information retrieval, we use a combination strategy that integrates words and n-grams at the ranked list level. In combining words and n-grams, we concentrate on generating several ranked lists showing different retrieval characteristics on word and n-gram indexes by incorporating feedback schemes. For cross-language information retrieval, we attempt a dictionary-based bi-directional combination of query translation and document translation. For both query translation and document translation, their naïve translation is used. Experimental evaluations on CJK monolingual and KC/KJ cross-language retrieval give promising results on our combination approaches: words vs. ngrams, and query translation vs. document translation.