Structured Query Formulation and Result Organization for Session

Complicated search such as making a travel plan usually requires more than one search queries. A user interacts with a search engine for multiple iterations, which we call a session. Session search is the task that deals with document retrieval within a session. A session often involves a series of interactions between the user and the search engine. To make use of all the queries and various interactions in a session, we propose an e ective structured query formulation method for session search. By identifying phrase-like textual nuggets, we investigate di erent degrees of importance for phrases in queries, aggregate them to create a highly e ective session-wise query, and send them to state-of-the-art search engine to retrieval the relevant documents. Our system participated in the TREC 2012 Session track evaluation and won the second position in whole session search (RL2-RL4). A second main contribution of this thesis is to increase stability of result organization for session search. Search result clustering (SRC) hierarchies are widely used in organizing search results. These hierarchies provide users overviews about their search results. Search result organization is usually sensitive to even slight change in queries. Within a session, queries are related and hence the search result organization should be related as well and maintain a more stable representation of the organization. We propose two monothetic concept hierarchy approaches that exploit external knowledge to build more stable SRC hierarchies for session search. One approach corrects