4.4 Adding Levels of Abstraction to Data Flow Modeling
Keeping the complexity of systems in view, data flow modeling technique has suggested disseminating information of a system in more then just one levels of abstraction. What are these levels, please see below for a discussion.
As we have already described that in data flow modeling only those processes can be expressed that perform certain processing or transformation of information. Now the question arises how far these processes need to be expressed? As a single process like Calculate Commission as described in the above section, can be described in sufficient detail such that all of its minute activities can be captured in the data flow diagram. However, if we start adding each bit of system functionality in a single data flow diagram, it would become an enormously large diagram to be drawn on a single piece of paper. Moreover, requirement analysis is an ongoing activity in which knowledge expands as you dig out details of processes. Therefore, it may not be possible for an analyst to know each bit of all the processes of the system from the very beginning.
Keeping the complexity of systems in view, data flow modeling technique has suggested disseminating information of a system in more then just one levels of abstraction. What are these levels, please see below for a discussion.
Context Level Data Flow Diagram
In a top-down system analysis, an analyst is required to develop high level view of the system at first. In data flow modeling, this high-level view is the Context level data flow diagram. In this diagram, system’s context is clarified such that all the external agents or entities with which the system interacts are captured. It captures the details of what information flows between the system and these external entities, and what outputs are generated against inputs from these external agents and so on. So, the analyst probes out all the external agents that may involve persons, organizations or other systems who directly interacts with this system and their specific involvement in the system. At this level, systems internal details are not exposed, as we want to see system behavior as a black box.
Next we will see Detailed Data Flow Diagrams.
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