1. Introduction to Design Patterns
By R.J. Lorimer
Sr. Object Oriented Architect
Schultz and Associates, Ltd.

2. What are Design Patterns
Design patterns are the definition for common formations and interactions among objects to solve common problems.
“The idea behind design patterns is to develop a standardized way to represent general solutions to commonly encountered problems in software development.” - (Stephen Stelting, Olav Maassen, Applied Java™ Patterns)
Today’s design patterns are object-oriented Software specific; they are not language specific.

3. History of Design Patterns
Christopher Alexander (the father of patterns) in the 1970’s produced many books that discussed the concept of software patterns.
Most popular, widely known patterns for object-oriented design defined in this book: “Design Patterns: Elements of Reusable Object-Oriented Software”. Original code excerpts were in C++.
Authored by: Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides.
Group commonly known as ‘the Gang of Four’, or ‘GoF’.
Many presentations and papers from conferences such as OOPSLA and JavaOne center around the concept of design patterns.

4. Why Design Patterns
Design Patterns can make difficult problems much simpler.
Using design patterns appropriately can make software more flexible in the future.
Patterns are often more recognizable to software specialists, making code more maintainable.
Design patterns are analyzed by many experts to reach a synthesis of reusability, flexibility, maintainability, and performance.

5. More on Design Patterns
Split into Categories: Creational, Behavioral, Structural, and System (optional).
Creational: Patterns that are involved in some way with object creation/construction.
Behavioral: Patterns that effectively provide some functionality in a modular and effective way.
Structural: Patterns that alter the composition of an object, thereby altering its functionality.
System: Patterns which provide some functionality that is typically useful at a higher level than other patterns. System-level patterns often act as a backbone to an application.

6. References Erich Gamma, Richard Helm, Ralph Johnson,John Vlissides
Design Patterns, Elements of Reusable Object-Oriented Software
Addison Wesley, 1995
ISBN
Stephen Stelting, Olav Maassen
Applied Java™ Patterns
Prentice Hall PTRPub, December 01, 2001
ISBN: