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Overview
The method adopted is to apply a process of functional decomposition in order to identify the principal processes and major data objects for the application. This method is then applied recursively to each process in order to identify successively smaller and simpler sub-processes. This exercise is continued to a level that resolves the application into logical functional modules. The functional model (specification) is then constructed from four principal elements. A Process Tree Diagram illustrating the major processes.- This provides a structured display of the hierarchy of processes, to resolve calling structures, code duplication, group process definitions, etc. A Functional Dataflow Diagram is constructed for each major process. This maps the flow of major data objects between the main processes of the application. A Process Definition is produced for each logical process identified. Tese are a series of high level descriptions of the functions required to satisfy the list of functional requirements A Data Definition is produced for each major data object. These act as the building blocks of the logical data model, screen or print definitions, etc. Screen Snapshots - give location where they can be found and method by which they were derived, e.g. WDESIGN. Details of the structure of these dialogues is not included as they may be refined or altered during the design and Build phase. Functional Prototypes: These consist of separate modules, illustrating the intended design, investigating alternative designs and algorithms and defining the methods to be used. The functional model does not include Concerns about data volumes Security measures - backup and recovery are left to the Implementation phase. Any reference to the physical code or data structures - these are dealt with as required in the Design and Build phase. No distinction is made between batch and on-line systems, except that the later, obviously, involves user interaction. At this stage the Design and Build phase has not yet detailed the final processing steps so detailed error message processing is unattainable
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