Norwegian University of Science and Technology Technical Report IDI-TR-8/2010 Exploiting Time-based Synonyms in Searching Document Archives

Recently a large number of easily accessible information resources have become available. To increase search quality, document creation time can be taken into account in order to increase precision, and query expansion of named entities can be employed in order to increase recall. A peculiarity of named entities compared to other vocabulary terms is that they are very dynamic in appearance, and synonym relationships between terms changes with time. In this paper, we present an approach to extract synonyms of named entities over time from the whole history of Wikipedia. In addition, we will use their temporal patterns as a feature in ranking and classifying them into two types, i.e., time-independent or time-dependent. Time-independent synonyms are invariant to time, while time-dependent synonyms are relevant to a particular time period, i.e., the synonym relation changes over time. Further, we describe how to make use of both types of synonyms in order to increase the retrieval effectiveness (precision and recall), i.e., query expansion with time-independent synonyms for an ordinary search, and query expansion with timedependent synonyms for a search wrt. temporal criteria. Finally, through an evaluation based on TREC collections we demonstrate how retrieval performance of queries consisting of named entity can be improved using our approach.