A data provision apparatus for providing site data to a service apparatus stores explanatory information for the site data including a specification of the site data, explanatory information of the service including the site data and a specification of the site data required by the service, and a rule for transforming the site data into that required by the service using the site data, the explanatory information of the site data, the explanatory information of the service, and the transformation rule being registered in advance; and refers to the explanatory information of the site data, the explanatory information of the service, and the transformation rule in response to a transfer request of the data from the service apparatus. All pieces of the site data used by the service are transformed into data of the specification required by the service and are transferred to the service apparatus.