Cross-language Information Retrieval with Explicit Semantic Analysis

We have participated on the monolingual and bilingual CLEF Ad-Hoc Retrieval Tasks, using a novel extension of the by now well-known Explicit Semantic Analysis (ESA) approach. We call this extension Cross-Language Explicit Semantic Analysis (CL-ESA) as it allows to apply ESA in a cross-lingual information retrieval setting. In essence, ESA represents documents as vectors in the space of Wikipedia articles, using the tfidf measure to capture how “important” a Wikipedia article is for a specific word. The interesting property of ESA is that arbitrary documents can be represented as a vector with respect to the Wikipedia article space. ESA thus replaces the standard BOW model for retrieval. In our cross-lingual extension of ESA, the cross-language links of Wikipedia are used in order to map the ESA vectors between different languages, thus allowing retrieval across languages. Our results are far behind the ones of other systems on the monolingual and ad-hoc retrieval tasks, but our motivation was to find out the potential of the CL-ESA approach using a first and unoptimized implementation thereof.