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Design pattern: Template Method

Description: "Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure."

This pattern can be used with both classes and prototypes.

The key for implementing this pattern is the message to self control construct, ::/1. It allows a predicate implementing an algorithm to call the predicates implementing the algorithm steps defined in descendant objects. It also allows easy definition of default definitions for the algorithm steps that can be inherited, redefined, or specialized in the descendant objects. The predicates implementing the algorithm steps are often declared as protected.