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Patterns and the language of patterns

From the Handbook for quality in cultural Web sites Improving quality for citizens, paragraph 2.5:

The principles of Usability, in as much as they are generic, are often difficult to apply and the Criteria that supply more detailed instructions can be interpreted in different ways or are tied to a specific technological area. These problems, though to a lesser extent, are also found in the application of GuideLines to Accessibility.

A different approach to the concrete problems of planning and realisation of Quality Web Sites is that of using Patterns to resolve recurring problems through noted and consolidated solutions. By now, the Web product has reached a degree of maturity such that the solutions to certain problems related to its use are considered common to all planners.

Furthermore, Patterns can be a useful reference point for those involved in Web site construction while not being experts. Indeed, in this case, Patterns can constitute a common language for communication between professionals to indicate what is required and why, regardless of how the solution is reached from the technical point of view.

Patterns neither eliminate nor substitute the need for involving users. On the contrary, by definition, they benefit from the concrete experience of users.

2.5.1 Definitions
The paradigm of Patterns was developed at the end of the ‘70’s by Christopher Alexander, professor of Architecture at the University of Berkeley in order to meet the complex problems related to urban planning and construction. According to Alexander, the poor quality of architecture in the ‘60’s was partly due to the lack of formal method in planning. He noted that urban planning and construction did not take concrete experience into account and the projects themselves were detached from the real needs of the users. This led to the idea of Patterns that establish relations between a context – a group of conditions or constraints tied to that context – and a solution which would resolve problems with those conditions and in that context.

From the mid ‘90’s, the idea of using the language of Patterns to assist planners, gained new credibility thanks to the enormous success of its application to the field of software engineering and “object oriented” planning. The paradigm of Patterns has recently been applied to the field of Human Computer Interaction (HCI), with extension to the world of the Web.

Patterns aim to provide a rigid method for describing a planner’s experience through formulating a solution to a common problem.

What characterises this approach is the choice to not give “pre-codified” solutions to the problem, but rather to try to accurately describe both the context and the solution, grouping the experience and the solutions adopted (also by other planners in similar experiences) together under the same title.


A Pattern is made up of three parts:

Context: this is the whole of the conditions and the surroundings, the environment of the action, all of the forces in action that the pattern has to consider and which constrain the choices of solution.

Problem: is a recurring situation in the context that creates imbalances between the forces at play.

Solution: is an algorithm, a piece of technology, an organisational structure, a well-known method, a model of reference which can resolve the recurring problem in that context.

It should be noted that a Pattern is made up of three parts: this implies that a problem alone is not a pattern, neither is a solution.

In a sentence: a Pattern is a proven solution to a recurring problem in a specific context.

Further elements are required to complete the definition of a pattern.

  • Name:a pattern must have a meaningful name. Naming something is the first step towards being able to communicate about it.
  • Conditions: descriptions of the conditions (or constraints) present in the context.
  • Notes: considerations (both positive and negative) on the consequences of the use of the current pattern (if any).
  • Related patterns: relations between the current pattern and other patterns used in the referral system (if any).
  • Known uses: detailed reference to practical applications of the current pattern (if any).

The language of Patterns groups together Patterns which work together to resolve problems in a given context.

The general context of reference to which we intend to apply the language of patterns, is the planning and realisation of Cultural Web Applications that must be Accessible and Usable – that is to say; of good quality.

Having established the common reference conditions, it is necessary to organise the Patterns in some way in order to use them.

Here it is proposed that a Catalogue of Patterns be created, with the aim of identifying general categories of problems to be faced. Within each of these categories, the patterns that define and resolve a particular problem will be placed.

Catalogue of patterns

Bibliography

Alexandex C. et al. A Pattern Language – Towns, Buildings, Construction. New York: Oxford University Press, 1977

Norman, Donald. The Design of Everyday Things. New York: Basic Books, 1988

Alexander Christopher. The Timeless Way of Building. New York: Oxford University Press, 1979

Cunningham, Ward – Beck, Kent. Using Pattern Languages for Object-Oriented Programs, presented to the Conference on Object-Oriented Programming, Systems, Languages, and Applications (OOPSLA), 1987

Gamma Erich – Helm, Richard – Johnson, Ralph – Vlissides, John. Design Patterns – Elements of Reusable Object-Oriented Software. Boston: Addison Wesley, 1995

Patter language for the web
http://c2.com/cgi/wiki?PatternLanguageForTheWeb

Tidwell, Jenifer, COMMON GROUND: A Pattern Language for Human-Computer Interface Design, 1999
http://www.mit.edu/~jtidwell/common_ground.html

Tidwell, Jenifer. UI Patterns and Techniques, 2002
http://time-tripper.com/uipatterns/

Van Welie, Martin, Interaction Design Patterns, 2001
http://www.welie.com/patterns/

© Minerva Project 2005-03, last revision 2005-03-06, edited by WP5, Committee for the development of a prototype of public cultural websites.
URL: www.minervaeurope/structure/workinggroups/userneeds/prototipo/progproto/architettura/pattern_e.html