How to design components

As usual, there is no one right way of doing this. However the main steps are regularly the followings:

• 1. Find the concepts/classes and their most fundamental relationships.
• 2. Refine classes by specifying the sets of operations on them. Classify these operations. In particular, consider the needs for construction, copying, and destruction. Consider minimalism, completeness, convience.
• 3. Refine classes by specifying their dependencies. Consider parametrization, inheritance and use dependencies
• 4. Specify the interfaces. Separate functions into public and protected operations. Specify the exact type of the operations on the classes.

These steps are in an iterative process. Typically, several loops through this sequence are needed to produce a design one can confortably use for an initial implementation or reimplementation.