1. An image processing apparatus for executing an application relevant to image processing, comprising: a request analyzing layer configured to analyze a user-specified request requesting a service, to determine whether the requested service requires a single application and does not involve the image processing or image editing by conveying a physical sheet of paper, or a workflow that includes combining together a plurality of function process units to perform the image processing by conveying the physical sheet of paper and performing at least one of scanning, printing, fax transmission and image editing, to send an instruction to a workflow control layer to form the workflow to be executed as the application, when it is determined that the requested service requires the workflow, and to send an instruction to an object corresponding to the single application to be executed as the application, when it is determined that the requested service requires the single application; and a processor that executes the application, wherein the workflow control layer is configured to control the workflow and create logic corresponding to the requested service by combining the plurality of function process units to serve as the application, the workflow control layer including: a document input/output request object that issues a request to objects in a lower level, each of which corresponding to one of the function process units included in the workflow, in order to conduct a series of processes in the workflow in response to an instruction from the request analyzing layer, and a process flow control unit configured to control an order in which the function process units of the workflow are to be executed.