TAILIEUCHUNG - Lecture Business system development - Lecture 11: Determining system requirements

In this chapter we will: Balance high-level and low-level DFDs; explain differences between current physical, current logical, new physical, and new logical DFDs; use DFDs for analyzing information systems; explain use cases and use case diagrams. | Business System Development CSC581 Lecture 11 Determining System Requirements 2 Summary of the previous lecture In previous lecture, we : Understood logical process modeling via data flow diagrams (DFDs). Drew DFDs of well-structured process models. Decomposed DFDs into lower-level diagrams. Outlines We today’s lecture we will: Balance high-level and low-level DFDs. Explain differences between current physical, current logical, new physical, and new logical DFDs. Use DFDs for analyzing information systems. Explain use cases and use case diagrams DFD Balancing The conservation of inputs and outputs to a data flow process when that process is decomposed to a lower level Balanced means: Number of inputs to lower level DFD equals number of inputs to associated process of higher-level DFD Number of outputs to lower level DFD equals number of outputs to associated process of higher-level DFD Unbalanced DFD This is unbalanced because the process of the context diagram has only one input .

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