Probabilistic Information Retrieval The document ranking problem We have a collection of documents User issues a query a list of documents needs to be returned Ranking method is core of an IR system In what order do we present documents to the user? We want the best document to be first second best second, etc Idea: Rank by probability of relevance of the document w.r.t information need P(relevant document, queryProbabilistic Information Retrieval 6 The document ranking problem ▪ We have a collection of documents ▪ User issues a query ▪ A list of documents needs to be returned ▪ Ranking method is core of an IR system: ▪ In what order do we present documents to the user? ▪ We want the “best” document to be first, second best second, etc…. ▪ Idea: Rank by probability of relevance of the document w.r.t. information need ▪ P(relevant|documenti , query)