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Define Logical Specifications

28 August, 2015 - 12:17

Review Question

Why do we study and document the current physical environment?


The first step the analysis team performs on the road to defining the logical specification is to study and document the current physical system. The team wants to build on the information available in the approved feasibility document and understand completely the current system operations. The team answers such questions as these. Given the system’s goals, what should the system be doing? Should the order entry system be supporting customer inquiries? What are the reasons the system is operating as it is? Why are there errors?

Review Question

Why do we develop a current logical model of an Information System?


After the current system has been documented with a physical data flow diagram, the team derives the current logical equivalent while removing all the physical elements from the diagram to produce a current logical data flow diagram, a description of the current logical system.

Working with the current logical system, the analysis team models the future logical system. Like the current logical DFD, the future logical DFD describes a system’s logical features. However, unlike the current diagrams, the future diagram describes what a system will do rather than what it presently does. To model what the new system will do, the team adds new activities, remodels existing activities, and adds or changes control activities. For example, in developing the Information System for the reengineered processes at Peapod, the development team would have modeled futureprocesses such as those that track the movement of groceries into and out of the distribution centers.

Review Question

Why do we develop alternative logical design?