1. An information processor to analyze the right of access to a database having a data file in a form of a structured document, the information processor comprising: a database storing an XML document; a preliminary access rights analysis device which decides, based on path expressions describing retrieval conditions used in retrieval for the database and an access control policy describing access control rules, to which one of 1) always permitted, 2) always denied, and 3) indeterminate access right in the database retrieval using the path expressions corresponds, said preliminary access rights analysis device deciding said access rights without retrieving said XML document if said access right is always permitted or always denied, and wherein if said access right is indeterminate, then said database retrieval system accessing said XML document to determine an access right; a query automaton generation unit for generating a query automaton from a path expression in which a retrieval condition for the database is described, wherein said path expression is extracted from a query requesting access to said database; an access control automaton generation unit for generating an access control automaton from an access control policy in which an access control rule is described; an operation unit having instructions for deciding access rights in database retrieval using the path expression by performing operations related to the query automaton generated by the query automaton generation unit and the access control automaton generated by the access control automaton generation unit, without accessing said data file stored in said database, said operation unit also having instructions for issuing a decision which allows access, or does not allow access, to said data in response to said query; a path expression extraction unit for extracting the path expressions from a query expression specifying a retrieval method for the database; and a query expression access right decision unit for deciding access rights in the database retrieval by the query expression based on decision results of access rights, which are obtained by the operation unit, for the individual path expressions extracted from the query expression.