A description of an
object-oriented design
technique which names, abstracts and identifies aspects of a
design structure that are useful for creating an
object-oriented design. The design pattern identifies
classes and instances, their roles, collaborations and
responsibilities. Each design pattern focuses on a particular
object-oriented design problem or issue. It describes when it
applies, whether it can be applied in the presence of other
design constraints, and the consequences and trade-offs of its
use.
http://st-www.cs.uiuc.edu/users/patterns/patterns.html.
["Design Patterns: Elements of Reusable Object-Oriented
Software", Erich Gamma, Richard Helm, Ralph Johnson, and John
Vlissides].