1. An apparatus which is provided on a server side on which various data is transmitted to or received from a client, and generates a document representing a Web page screen indicating data provided for the client, comprising: a data object storage unit storing a data object having data to be provided for the client and is provided with an interface representing a data structure of the data; a definition sentence storage unit storing a definition sentence defining a displaying method on the Web page screen about the data of the data object; a document generation unit generating a document representing a Web page screen on which the data is displayed with the data of the data object associated with the definition sentence based on the interface provided in the data object; a request obtaining unit obtaining a request containing data input to an input form shown on a Web page screen represented in a document generated by said document generation unit, said request being transmitted from the client; and a data update unit updating data, into data contained in the request, at a specified position in a data structure represented by an interface specified by a character string based on the character string contained in the request with the data and contained in the document generated by said document generation unit based on the character string comprising a character string specifying an interface as a base of generation of the document and a character string indicating a specific position in the data structure represented by the interface.