The present invention has a plurality of objects each holding state data as its attribute data, and employs the following steps: an object structure management means searches for an object based on an object identifier; an attribute data input/output means updates attribute data of the object by use of changed state data; and when a remote display system has issued an attribute data retrieval request, the object structure management means searches for an object based on an object identifier included in the attribute data retrieval request, and the attribute data input/output means retrieves attribute data of the object and returns it.