CLEF 2005: ad hoc track overview

We describe the objectives and organization of the CLEF 2005 ad hoc track and discuss the main characteristics of the tasks offered to test monolingual, bilingual, and multilingual textual document retrieval. The performance achieved for each task is presented and a statistical analysis of results is given. The mono- and bilingual tasks followed the pattern of previous years but included target collections for two new-to-CLEF languages: Bulgarian and Hungarian. The multilingual tasks concentrated on exploring the reuse of existing test collections from an earlier CLEF campaign. The objectives were to attempt to measure progress in multilingual information retrieval by comparing the results for CLEF 2005 submissions with those of participants in earlier workshops, and also to encourage participants to explore multilingual list merging techniques.