Patterns

Latest revision as of 06:06, 27 September 2009

What began as design patterns has grown into a diverse movement, including antipatterns, architectural patterns, organisational patterns etc.

What is a Pattern?

A pattern is an abstract representation of a solution to some form of problem. A pattern will detail the current situation, the cases where the pattern is applicable, the benefits and disadvantages of the pattern, other related patterns and the way of adding/changing code to apply pattern.

Types of Patterns

Pattern Families

This section is a starting point for the various families of patterns. These are the most well defined categories in the current literature.

• Design patterns - Patterns directly related to the composition and design of OO systems. These must be applicable to multiple domains (horizontal).
• Architectural patterns - Patterns specifically concerning architecting OO programs.
• Analysis patterns - Patterns related to a specific domain (vertical).
• Antipatterns - Patterns that detail a problem in an existing program and the solution.
• Amelioration patterns - Provide remedies to exiting code.
• Organisational patterns - Patterns around process and team management. (aka Management patterns)

Vertical vs Horizontal

This concept is proposed by a number of authors, including William Brown 1998.

• Vertical patterns are those that apply to a single domain (i.e. Analysis Patterns).
• Horizontal patterns are those that apply across domains.

Are the families different?

While authors have previously argued that all of these families of patterns are different, there is a growing thought that they contain many strong similarities to each other. There may be cases where certain families are actually not a logical distinction to draw.

• Antipatterns & Amelioration patterns are arguably the same thing, both detail an existing problem and a solution. They both require an existing body of code.
• Design patterns & Architectural patterns are arguably an overlapping set of patterns. Potentially a distinction can be made at the level of abstraction at which they are used.
• Antipatterns & Design patterns - Potentially, these two areas of patterns have a large area of overlap. The only obvious difference is that Antipatterns require an existing problem that has already had an attempt at implementation, Design patterns require a problem at any stage of the design process to be used.