XML descriptive commands corresponding to an application of another device utilized on network can be easily generated. A digital multifunctional device is an embodiment of an image processing apparatus and is connected to network devices, such as a FAX server and a document server, via the network. The digital multifunctional device obtains a registered schema corresponding to an application of another network device such as a FAX server. When another network device is utilized, commands described in the XML is generated by using the obtained schema, and the commands are transmitted to appropriate network device along with image data to be processed. The network device receiving the image data and the commands executes predetermined processing in accordance with the commands.