Blind Relevance Feedback and Named Entity based Query Expansion for Geographic Retrieval at GeoCLEF 2006

The participation of the University of Hildesheim focused on the monolingual German and English and the bilingual German English tasks of GeoCLEF 2006. Based on the results of GeoCLEF 2005 the weighting and expansion of geographic named entities (NE) within a Boolean retrieval approach were combined. Since the best results 2005 were achieved with Blind Relevance Feedback (BRF), in which NEs seemed to play a crucial role, the effects of adding particular geographic NEs within the BRF are also explored. The paper presents a description of the system design, the submitted runs and preliminary results. A first analysis especially of inofficial post experiments indicates that geographic NEs can improve BRF and supports prior findings that the geographical expansion within a Boolean retrieval approach does not necessarily lead to better results – as is often assumed. The discussion is followed by planned future research activies.