Johnson and Foote's heuristics

In their text, Johnson and Foote 1988, Johnson & Foote describe a number of important heuristics.

Rules for Finding Standard Protocols

These heuristics determine a set of rules that standardising class design and structure.

• Rule 1: Recursion introduction
• Rule 2: Eliminate case analysis
• Rule 3: Reduce the number of arguments
• Rule 4: Reduce the size of methods

Rules for Finding Abstract Classes

These heuristics define methods of determining and extracting abstract classes.

• Rule 5: Class hierarchies should be deep and narrow
• Rule 6: The top of the class hierarchy should be abstract
• Rule 7: Minimize accesses to variables
• Rule 8: Subclasses should be specializations

Rules for Finding Frameworks

The heuristics describe how to find frameworks in OOD.

• Rule 9: Split large classes
• Rule 10: Factor implementation differences into subcomponents
• Rule 11: Separate methods that do not communicate
• Rule 12: Send messages to components instead of to self
• Rule 13: Reduce implicit parameter passing

External Resources

• Designing Reusable Classes - A summary