Summary

1. System design is a transition from a user-oriented document to a document oriented to programmers or data base personnel. It goes through logical and physical design with emphasis on the following:

   a. Preparing input/output specifications.

   b. Preparing security and control specifications.

   c. Specifying the implementation plan.

   d. Preparing a logical design walkthrough before implementation.

   2. Structured design is a data-flaw-based methodology that identifies in­ puts and outputs and describes the functional aspects of the system. It partitions a program into a hierarchy of modules organized in a top­ down manner with the details at the bottom.

   3. The documentation tool is the structure chart. It has three elements­ the module, the connection, and the couple. When a module is evaluated, the module's connections to other modules (coupling) and its intramodule strength (cohesion) are considered.

   4.One way of developing an input process/output chart for modules is with the HlPO chart. It consists of the hierarchy chart plus the input process/output (IPO) chart, thus capturing the essence of top-down decomposition. The aids are the HlPO work sheet and template.

   5. A useful activity in all phases of a structured project is the walkthrough where ideas are interchanged among peers. User involvement is extremely important.

   6. The major development activities during structured design are data base design, implementation planning, system test planning, system interface specifications, and user documentation. Much of the documentation is written after conversion, a task that follows design.

   7. A well-designed system should provide for controls to eliminate errors check fraud, and ensure system integrity. Audit trails, documentation and processing control must be incorporated into the system before- it is released to the end user.