As indicated by Jackson, in order to create a generator to generate an efficient program structure which uses data flow for its constraint computations, we should detect and solve the problem of the clash of input-output data structures. This paper proposes a general frame-work to characterize the problem of structure clash in the creation of generator for architectural CAD system. This framework employs a method using relational inference to detect ordering clash, and at the same time determine the execution sequence of generated procedural program. Moreover, the paper describes an implementation of this method for generating an object-oriented program of CAD system in the domain of architecture.