When software developers mention design patterns, the chances are that they are talking about Design Patterns, the classic book by the Gang of Four, rather than design patterns in general. Even when they are talking about the pattern concept, as opposed to specific patterns, they often think in terms of the form and idea presented in GoF, and rarely beyond.
Since the publication of the seminal work by the GoF in 1994, however, a great deal of research and practice in patterns has led to a better understanding of both the pattern concept and the strengths and weaknesses of the GoF patterns themselves.
This tutorial revisits the GoF patterns, reflects on them, deconstructs them, and re-evaluates them from the practitioner's perspective: why patterns such as Abstract Factory, Builder, Flyweight, Command, and others are missing a vital ingredient to be proper parts of an architectural vocabulary; why Iterator is not always the best solution for traversing aggregates; why State is not the only state pattern; why some patterns, such as Bridge, are more than one pattern; and what you can do about it.
Prerequisites: Sound knowledge of the pattern concept and the GoF patterns are required.
Frank Buschmann is senior principal engineer at Siemens Corporate Technology in Munich, Germany. His interests include Object Technology, Frameworks and Patterns. Frank has been involved in many software development projects. He is leading Siemens' pattern research activities. Frank is co-author of "Pattern-Oriented Software Architecture -- A System of Patterns" and "Pattern-Oriented Software Architecture -- Patterns for Concurrent and Networked Objects".
Kevlin Henney is an independent consultant and trainer. The focus of his work is in programming languages, OO, CBD, UML, patterns, and software architecture. He is a regular columnist for C/C++ Users Journal (online), Application Development Advisor (UK), and JavaSpektrum (Germany), and previously wrote columns in Java Report and C++ Report. He is also a member of the advisory board for Hillside Europe, the program chair for EuroPLoP 2003, and a popular speaker at conferences in the US and Europe.