A computer implemented method of indexing a plurality of responses for later retrieval and presentation to a user in response to queries, includes, for each of the plurality of responses, receiving at least one representative query for that response. The representative query(s) represent text (e.g. natural language) query(s) to be input by an end user searching for information addressed by that response. Each representative query is parsed into terms. The terms are analyzed to determine which of these terms are more likely to uniquely identify queries for the particular response among terms in representative queries for all indexed responses. Boolean expression(s) satisfied by a text query containing one of the terms determined to more likely uniquely identify that response, and another one of the parsed terms are formed.