User:JarlvonHoother

Yes this is JarlvonHoother. Who do you be?

Vail Place is a non-profit agency that provides essential recovery oriented services for people in Hennepin County with long term mental illnesses. Vail Place is a clubhouse built around the The Clubhouse Model of Psychosocial Rehabilitation.

Units
Clerical Unit Main Unit Food Service Unit

Services
Housing Employment

Experimental
In software engineering, a design pattern is a general reusable solution to a commonly occurring problem in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Algorithms are not thought of as design patterns, since they solve computational problems rather than design problems.

Not all software patterns are design patterns. Design patterns deal specifically with problems at the level of software design. Other kinds of patterns, such as architectural patterns, describe problems and solutions that have alternative scopes.

History
Patterns originated as an architectural concept by Christopher Alexander (1977/79). In 1987, Kent Beck and Ward Cunningham began experimenting with the idea of applying patterns to programming and presented their results at the OOPSLA conference that year. In the following years, Beck, Cunningham and others followed up on this work.

Design patterns gained popularity in computer science after the book Design Patterns: Elements of Reusable Object-Oriented Software was published in 1994 (Gamma et al.). That same year, the first Pattern Languages of Programming Conference was held and the following year, the Portland Pattern Repository was set up for documentation of design patterns. The scope of the term remains a matter of dispute. Notable books in the design pattern genre include:



Although the practical application of design patterns is a phenomenon, formalization of the concept of a design pattern languished for several years.

Uses
Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems, and it also improves code readability for coders and architects who are familiar with the patterns.

Often, people only understand how to apply certain software design techniques to certain problems. These techniques are difficult to apply to a broader range of problems. Design patterns provide general solutions, documented in a format that doesn't require specifics tied to a particular problem.

Design patterns are composed of several sections (see Documentation below). Of particular interest are the Structure, Participants, and Collaboration sections. These sections describe a design motif: a prototypical micro-architecture that developers copy and adapt to their particular designs to solve the recurrent problem described by the design pattern. A micro-architecture is a set of program constituents (e.g., classes, methods...) and their relationships. Developers use the design pattern by introducing in their designs this prototypical micro-architecture, which means that micro-architectures in their designs will have structure and organization similar to the chosen design motif.

In addition, patterns allow developers to communicate using well-known, well understood names for software interactions. Common design patterns can be improved over time, making them more robust than ad-hoc designs.

Domain specific patterns
Efforts have also been made to codify design patterns in particular domains, including use of existing design patterns as well as domain specific design patterns. Examples include User Interface design patterns, Information Visualization and web design.

The Pattern Languages Of Programming Conference(annual,1994->) proceedings includes many for examples of domain specific patterns.

Caveats
In order to achieve flexibility, design patterns usually introduce additional levels of indirection, which might complicate the resulting designs and hurt application performance.

Classification
Design Patterns originally grouped design patterns into the categories Creational Patterns, Structural Patterns, and Behavioral Patterns, and described them using the concepts of delegation, aggregation, and consultation. For further background on object-oriented design, see coupling and cohesion. For further background on object-oriented programming, see inheritance, interface, and polymorphism.

Documentation
The documentation for a design pattern describes the context in which the pattern is used, the forces within the context that the pattern seeks to resolve, and the suggested solution. There is no single, standard format for documenting design patterns. Rather, a variety of different formats have been used by different pattern authors. However, according to Martin Fowler certain pattern forms have become more well-known than others, and consequently become common starting points for new pattern writing efforts. One example of a commonly used documentation format is the one used by Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides (collectively known as the Gang of Four) in their book Design Patterns. It contains the following sections:


 * Pattern Name and Classification: A descriptive and unique name that helps in identifying and referring to the pattern.
 * Intent: A description of the goal behind the pattern and the reason for using it.
 * Also Known As: Other names for the pattern.
 * Motivation (Forces): A scenario consisting of a problem and a context in which this pattern can be used.
 * Applicability: Situations in which this pattern is usable; the context for the pattern.
 * Structure: A graphical representation of the pattern. Class diagrams and Interaction diagrams may be used for this purpose.
 * Participants: A listing of the classes and objects used in the pattern and their roles in the design.
 * Collaboration: A description of how classes and objects used in the pattern interact with each other.
 * Consequences: A description of the results, side effects, and trade offs caused by using the pattern.
 * Implementation: A description of an implementation of the pattern; the solution part of the pattern.
 * Sample Code: An illustration of how the pattern can be used in a programming language
 * Known Uses: Examples of real usages of the pattern.
 * Related Patterns: Other patterns that have some relationship with the pattern; discussion of the differences between the pattern and similar patterns.

Criticism
In the field of computer science, there exist some criticisms regarding the concept of design patterns.

Unlike components, does not provide reuse
A pattern must be programmed anew into each application that uses it. Some authors see this as a step backward from software reuse as provided by components. This observation has led to work on "componentization": turning patterns into components, in particular by Meyer and Arnout, who claim a 2/3rds success rate in componentizing the best-known patterns.

Workarounds for missing language features
Users of dynamic programming languages have discussed many design patterns as workarounds for the limitations of languages such as C++ and Java. For instance, the Visitor pattern need not be implemented in a language that supports multimethods. The purpose of Visitor is to add new operations to existing classes without modifying those classes -- but in a language with multimethods, methods are not part of the class structure. Similarly, the Decorator pattern amounts to implementing dynamic delegation, as found in Objective-C and Self.

Peter Norvig, in Design Patterns in Dynamic Programming, discusses the triviality of implementing various patterns in dynamic languages. Norvig and others have described language features that encapsulate or replace various patterns that a C++ user must implement for themselves.

Does not differ significantly from other abstractions
Some authors allege that design patterns don't differ significantly from other forms of abstraction, and that the use of new terminology (borrowed from the architecture community) to describe existing phenomena in the field of programming is unnecessary. The Model-View-Controller paradigm is touted as an example of a "pattern" which predates the concept of "design patterns" by several years. It is further argued by some that the primary contribution of the Design Patterns community (and the Gang of Four book) was the use of Alexander's pattern language as a form of documentation; a practice which is often ignored in the literature.