A method of learning user query concept for searching visual images encoded in computer readable storage media comprising: providing a multiplicity of sample images encoded in a computer readable medium; providing a multiplicity of sample expressions that correspond to sample images and in which terms of the sample expressions represent features of corresponding sample images; defining a user query concept sample space bounded by a boundary k-CNF expression and by a boundary k-DNF expression refining the user query concept sample space by, soliciting user feedback as to which of the multiple presented sample images are close to the user's query concept; removing from the boundary k-CNF expression disjunctive terms based upon the solicited user feedback; and removing from the boundary k-DNF expression respective conjunctive terms based upon the solicited user feedback.