Design Patterns-reusable basics of object-oriented software (1.1) What is a design pattern?

1. four essential elements of a pattern:
(1) pattern name;
(2) problem;
(3) solution;
(4) consequences: the results and trade-offs of applying the pattern.

2. One person's pattern can be another person's primitive building block.

3. The design patterns in this book are descriptions of communicating objects and classes that are customized to solve a general design problem in a participant context.

4. In Design with procedural laugnages, "inheritance", "encapsulation" and "polymorphism" can also be design patterns.