1. A method of retrieving a desired document item or information item from a plurality of document items and/or information items, items being identified by item index vectors, the method being performed in response to a query including plural query terms, the query terms being related to each other in Boolean logic form, the method comprising transforming the query terms in Boolean logic form into a transformed vector form, and retrieving the desired item information in response to similarity measurements of the transformed vector form of the query terms and the item index vectors.