Deliverable I – E-R Diagram
The E-R Diagram should be developed through a step-by-step process. The steps that will be followed are listed below:
- A listing of objects (potential entities) on a process-by-process and/or report-by-report basis.
- A listing of attributes for the entities and composite entities.
- E-R diagram showing connectivity, optional/mandatory, weak entities, etc.
This system, although only a simulated company and quite scaled down, is still too large and too complex for inexperienced designers to grasp in its entirety. At least, that was the point when I designed the case.
When a system is too large to deal with easily, what approach do you use?
The first thing that should occur to you was a topic mentioned in Systems
Analysis and Design – modular design. Whenever you start developing a
system one of your first concerns should be
whether you can modularize it to reduce cognitive complexity. One Systems
Analysis and Design lecture pointed out that
A modular approach involves
breaking the system into logical, manageable portions, or modules.
So if you break the Lost River Wind Riders into modules, the most obvious ones include Sales, Service, and Restocking. Each of those is a manageable subsystem to consider.
Using that as a starting point, you need to analyze each subsystem in terms of the approach that we used for the example in class. List business functions (or forms and reports) for each subsystem, list the objects under each, refine the list by applying the definition for entity, then develop an ER diagram for each subsystem. When you have three ER diagrams, consolidate the three into a single ERD by determining the overlap between each.
The concepts that we cover in this class are simple, but applying them can be a bit tougher. Work together with your team. Don't assign one individual to one task, another to something different, etc. That might work if you really knew what you were doing, but...