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? 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.
We are now at the point to describe how the new system will operate. Working with the future logical system, an analysis team could devise several physical alternatives.
1. The first step in developing a future physical system is to decide which processes will be manual and which will be automated.
2. As a second step in developing an alternative physical design, the analyst must decide which processes will begin immediately upon occurrence of an event and which will only operate periodically.