Using Geographic Signatures as Query and Document Scopes in Geographic IR

Abstract

Abstract. This paper reports the participation of the University of Lisbon at the 2007 GeoCLEF task. We adopted a novel approach for GIR, focused on handling geographic features and feature types on both queries and documents, generating signatures with multiple geographic concepts as a scope of interest. We experimented new query expansion and text mining strategies, relevance feedback approaches and ranking metrics.

Experiments with Geographic Evidence Extracted from Documents

“…The expanded geographic terms are then re-weighted according to the graph distance in the ontology between the node associated to the expanded concept and descendent nodes by the formula 1 distance−1 . For the given example, USA generates 50 states with a weight of 1 2 and several cities with weight 1 3 (considering that the node distance in the ontology between states and countries is 1, and between cities and countries is 2). The final geographic terms represent the query geographic signature(Q sig ).…”

“…In fact, placenames revealed to be good retrieval terms, and were frequently ranked at the top on the query expansion step [1]. While placenames may be used in other unrelated contexts, such as proper names, they seem to help recall when used as plain terms.…”

“…Following a thorough analysis of the results achieved on the 2007 participation [1], we identified the following improvement points:…”

“…Capture more geographic evidence from documents. The text mining module, based on shallow pattern matching of placenames, often failed on the extraction of essential geographic evidence for geo-referencing many relevant documents [1]. We therefore considered reformulating our text annotation tools, making them capable of capturing more geographic evidence from the documents.…”

“…Used as a text annotation tool, REMBRANDT generates more comprehensive geographic document signatures (D sig ). We first introduced D sig on last year's participation [1] as a means to capture the geographic scope of documents as lists of geographic concepts corresponding to the grounded names in the documents used for computing the geographic similarity of documents and queries. The D sig comprise two kinds of geographic evidence: i) explicit geographic evidence, consisting of grounded placenames that designate locations, and ii) implicit geographic evidence, consisting of other grounded entities that do not designate explicitly geographic locations but are strongly related to a geographic location (e.g., monuments, summits or buildings).…”