1. A document management system for referencing document data from among multiple document data gathered in response to a referencing request from a document referencing part connected via a network, said system comprising: a storing part for storing said multiple document data; a receiver part for receiving from said document referencing part, transmission of identifying information that identifies a first document data included amongst said multiple document data, transmission of a request to perform a referencing operation for document data with the appropriate relationship to said first document data and transmission of referencing conditions that provide the conditions for said referencing operation; a processing part that is connected to said receiving part and to said storing part that, in accordance with a previously stored program and based on said request for performance of a referencing operation, utilizes said identifying information and executes a referencing operation for document data having the appropriate restricted relationship with said first document data in accordance with information defining the appropriate relationship to said first document data, which processing part selects as a result of its referencing operations and from among said document data referenced for having said appropriate relationship, that document data which fulfills said referencing conditions for said information defining the appropriate relationship; and an output part that is connected to said processing part and to said network that outputs to said network said selected results of referencing operations.