IBM i General Design Standards › Design Methods

Design Methods

When you start to design your system, apply the following basic principles:

• Use the computer as much as possible:

  - Many aspects of the design process can be done automatically.

  - You can use the computer to index and organize the design.

  - You can repeatedly modify the design with minimum effort.

  - You can use any existing designs.

  - You can easily document the design.

  - The results of the design can be carried through to implementation without re-keying.

  - You can improve the quality.

  - Use CASE tools, generators, and word processors wherever possible.

• Present designs to the end user and reach agreement before programming starts. This is because:

  - You must understand what the user wants; the only way you can verify user requirements is to restate your interpretation for verification.

  - It is cost effective to incorporate changes before programming has begun.

Use prototyping and modeling tools wherever possible:

• Use standards to reduce the complexity of the design problem. Omit features of appearance or performance from the specification that are covered by standards. This allows you to:

  - use existing design work

  - achieve more consistent user interface

  - improve quality

Use design and generator tools that enforce standards:

• Ensure that all systems have a consistent user interface—consistent internally within the application, with SAA CVA standards, and with the OS/400 system interfaces that will be common to all applications. This:

  - reduces the amount of work required to specify a system

  - simplifies the process of learning how to use the system

Use automatic layout tools:

• Recognize that the design process is both iterative and experimental. It will require several passes to try out solutions, explore connections, and allow for user feedback.

Use prototyping and modeling tools:

• Design in as modular a manner as possible so that you can develop and test each part of the system separately, and so that you can repeatedly use commonly required functions.
• Use a systematic method for those processes that cannot be entirely computer-based, such as testing. The computer can be used to organize the systematic method.