US Patent 7949657 Detecting zero-result search queries

A processing device and method may be provided for determining whether a zero search result may be produced with respect to a search for a document including all words of a word group. An index, with respect to words included in a group of documents, may be searched for documents including all words of the word group when a zero search result is determined not likely to occur with respect to the search for the document including all of the words of the word group. A method for creating multiple types of data structures corresponding to word grouping collections may further be provided to store occurrence information indicating a likelihood of a presence of a document including all words of a word group.