Supporting user query reformulation and searching: a concept hierarchy approach

While technological advances have enabled us to access extensive document col lections, formulating a query which is well designed for an information retrieval (IR) system remains a difficult task. A number of methods have been developed to support user query formulation and reformulation based on terminological feed back. Terminological feedback offers a set of terms that can be used to modify an existing query. This also gives users an opportunity to transform a part of the query re/formulation process to term selection: a potentially simpler task. There is, how ever, much room for investigating and improving the interaction between users and IR systems with regard to query re/formulation. The limited context and structure of suggested terms are just some of the problems found with existing methods. This thesis presents a new approach to supporting user query reformulation and searching. The approach is based on hierarchical organisation of terms, which is dynamically derived from a set of retrieved documents. This thesis investigates both statistical and lexical aspects of terms as a means of deriving a hierarchy from texts. As a summative evaluation of our approach, a user study is carried out to investigate several aspects of the user interaction with our support system. A search interface is developed to integrate a visualised hierarchy into a search result of an IR system. Two types of hierarchies are evaluated based on a TREC test collection, and compared to a baseline that has no hierarchy. Results suggest that multiple aspects of information searching process can be supported by the hierarchies. In particular, the range of search vocabulary employed to complete a task is shown to increase, and browsing of retrieved documents is found to be facilitated by the hierarchies.