A sort of "BestPracticesDocument?" set, dealing with a problem to which there is no clear single solution, and the means to arrive at any of a number of acceptable solutions.
Each "Page" of a classic Pattern Language has:
Christopher Alexander http://www.patternlanguage.com/ defines a 'pattern' as a three-part construct. First comes the 'context' - the conditions under which this pattern holds. Next is a 'system of forces'. In many ways, it is natural to think of this as the 'problem' or 'goal.' The third part is the 'solution' - a configuration that balances the system of forces or solves the problems presented.
Generally a PL will also have:
Cool possible Pattern Languages ("how-tos") for this wiki could include: