A business program in an XML driven architecture is disclosed. XML data corresponding to a form screen is analyzed and a business class corresponding to a tag included in the XML data is specified. By referring to a business class manager in which the business classes to be created are registered, it is judged whether the business class has been registered, and if the specified business class has not been registered, the specified business class is registered. After this, each of the business classes has to be specifically programmed. At the execution time of the programmed business classes, XML data including tags is obtained, and the business classes that correspond to the tags included in the XML data and are programmed carry out a processing relating to the tags. Then, the specified business classes are called among the business classes that are defined in advance and loaded in a memory.