Experiments with Geo-Temporal Expressions Filtering and Query Expansion at Document and Phrase Context Resolution

We describe an evaluation experiment on GeoTemporal Document Retrieval created for the GeoTime evaluation task of NTCIR 2010. GeoTemporal Retrieval aims at to improve retrieval results using Geographic and Temporal dimensions of relevance. To accomplish that task, systems need to extract geographic and temporal information from the documents, and then explore semantic relations among those dimensions within the documents. Since this is the first time the task is taking place our aim is to evaluate some basic techniques in order to set some research directions of our work. We aim to understand the relevance of temporal and geographic expressions for filtering purposes. The geographic expressions were extracted with Yahoo PlaceMaker and for temporal expressions we used the TIMEXTAG system. We experimented techniques using both the overall document and sentence resolutions, as also one mixed approach. We also used a query expansion mechanism in topics with no filters defined. We used the BM25 as retrieval model and preprocessed the topics with a semi-automatic methodology to create structures that let us create our filters and expansions. We learned that the sentence level is not a very good approach (but we got clues that probably the paragraph context resolution could improve the results) and the geographic and temporal expressions base filters had shown good performance.