Terry, Chuck and all,
Comment on validation of design patterns.
I agree that it is a problem to validate patterns. Most pattern collections (usually more
collections than languages) tend to be based on rather sloppy research. They are usually
just documentation of what usually works in different situations. Alexander's patterns (in
A Pattern Language) often lack a firm grounding in evidence.
To validate a pattern I would start by establishing that the field of forces the pattern
describes actually exists in the situation it portrays. Triangulation of methods is probably
useful here. Then I would try to verify that the problem is real: that forces in the pattern
actually are in conflict if the solution feature isn't present. Finally we come to the tricky
part: Validating the solution feature of the pattern. We could probably conduct (field)
experiments to see if it solves the conflicting forces or if (as Alexander would put it) they
spill over to surrounding patterns, but we seldom do. If we did, it would merit the pattern
two asterisks in Alexander's format. Instead, i think it is common to base it on
observations that inductively support the solution (this would merit it one asterisk). Here
we must remember that a pattern is nothing more than a clearly stated and debatable
working hypothesis of what we currently know to be the best arrangement for solving to
a recurring problem.
Given that a pattern is a working hypothesis it probably should be tested as one
(experimentally). Building well-founded and evidence-based patterns is like building
theory: a constant flux between inductive and deductive research.
However, we may wish to do inspirational patterns. Not meant to be based on evidence
of what works, but instead inspire people to find new solutions. Such patterns are not
evidence based, and talking about validation of them is probably not the right word. Jonas
Löwgren has written a paper on such inspirational patterns:
Löwgren, J. (2007). Inspirational patterns for embodied interaction. Journal of Knowledge,
Technology & Policy 20(3):165–177.
Cheers,
// Mattias
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MATTIAS ARVOLA, Ph.D.
Sr. lecturer in Interaction Design.
Linköping University and Södertörn University.
www.arvola.se
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