Patent ID: 7287025

Claim:
A computer-based method for query expansion, the method comprising: extracting new terms from a newly submitted query; identifying expansion terms for adding to the new terms prior to submission to a search engine for retrieval of a relevant document list, the expansion terms being identified at least in part on the new terms and probabilistic correlations from information in a query log; wherein the information comprises one or more query terms and a corresponding set of document identifiers (IDs), the query terms having been submitted to a search engine, the document IDs represent each document selected from a list generated by the search engine responsive to searching for information relevant to corresponding ones of the query terms; presenting the relevant document list to a user; and wherein identifing expansion terms further comprises: selecting particular ones of the document terms that correspond to the new terms according to the following: P ⁢ ( w j ( d ) | w i ( q ) ) = ∑ ∀ D k ∈ S ⁢ ( W jk ( d ) × f ik ( q ) ⁡ ( w i ( q ) , D k ) f ( q ) ⁡ ( w i ( q ) ) ) , wherein w j (d) and w i (q) are an arbitrary document term and query term respectively, and P(w j (d) |w i (q) ) is defined as follows: P ⁡ ( w j ( d ) | w i ( q ) ) = ⁢ P ⁡ ( w j ( d ) , w i ( q ) ) P ⁡ ( w i ( q ) ) = ⁢ ∑ ∀ D k ∈ S ⁢ ⁢ P ⁡ ( w j ( d ) , w i ( q ) | D k ) × P ⁡ ( D k ) P ⁡ ( w i ( q ) ) = ⁢ ∑ ∀ D k ∈ S ⁢ ⁢ P ⁡ ( w j ( d ) , w i ( q ) , D k ) P ⁡ ( w i ( q ) ) = ⁢ ∑ ∀ D k ∈ S ⁢ ⁢ P ⁡ ( w j ( d ) | w i ( q ) , D k ) × P ⁡ ( w i ( q ) , D k ) P ⁡ ( w i ( q ) ) = ⁢ ∑ ∀ D k ∈ S ⁢ ⁢ P ⁡ ( w j ( d ) | D k ) × P ⁡ ( D k | w i ( q ) ) × P ⁡ ( w i ( q ) ) P ⁡ ( w i ( q ) ) = ⁢ ∑ ∀ D k ∈ S ⁢ ⁢ P ⁡ ( w j ( d ) | D k ) × P ⁡ ( D k | w i ( q ) ) , and wherein S is a set of documents, P(D k |w i (q) ) is the conditional probability of the document D k being selected in case that w i (q) appears in the user query, P(w j (d) |D k ) is the conditional probability of occurrence of w j (d) if the document D k is selected, P(D k |w i (q) ) is statistically obtained from the query log, P(w j (d) |D k ) is a function of frequency of occurrence of w j (d) in a document D k , as well as the occurrence of the term w j (d) in all documents identified in the user log.