A Belief Model of Query Diculty that uses Subjective Logic

Abstract. The diculty of a user query can a↵ect the performance of Information Retrieval (IR) systems. This work presents a formal model for quantifying and reasoning about query diculty as follows: Query diculty is considered to be a subjective belief, which is formulated on the basis of various types of evidence. This allows us to define a belief model and a set of operators for combining evidence of query diculty. The belief model uses subjective logic, a type of probabilistic logic for modeling uncertainties. An application of this model with semantic and pragmatic evidence about 150 TREC queries illustrates the potential flexibility of this framework in expressing and combining evidence. To our knowledge, this is the first application of subjective logic to IR.