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Patterns capture the design knowledge of experts. But how is this expertise represented by the expert? When we mine for patterns, what is the ground in which we seek? Are there patterns in our head? And if so, how do the patterns in our head relate to the design patterns in the real world and the patterns we document? This paper tries to give some answers by referring to the principles of psychological schema theory. Schemas are some sort of patterns in our heads. A special type of schema, the problem schema, has many features in common with design patterns. The paper will discuss how schemata are organized in memory, how they are activated and constructed. At the end, we will discuss implications for the mining of patterns.
Yann-Gaël Guéhéneuc, 2013/09/20
The paper makes very interesting links between design patterns and schema theory, which is one theory to explain memory and its ability to recognise and use “schema” efficiently. It does not go into the reasons why our memory would use schema (probably from our evolution from hunters-gatherers…) but how this theory about the “conceptual model of human memory” explains our like of design patterns and some implications. Also, “[i]t does not make any statement about the nature of reality, that is whether these ``real forms”“ [document by patterns] exist in an objective reality or in a socially/individually constructed reality”.
First, the paper recalls briefly the history of schema theory, starting from Plato and Aristotle (!) who spoke of the “essence or nature of things” all to recent works by Barlett, who focused on “how schemas are acquired, applied, stored, and manipulated in memory, passing by Kant, for whom “a schema was the link from empirical information to the pure categories or concepts” in memory.
Second, the paper makes it clear that ”[a] pattern does not exist as a real thing, because real things can only manifest patterns“ and that ”[l]ike patterns, a problem schema “allows problem solver to group problems into categories in which the problems in each category require similar solutions”“. Schema are “mental representations in an individual's mind”, which “bundles all experience within one class”, “abstracting away from irrelevant or superficial variations of these experiences”. The schema are used by the brain to “recognise similar and discriminate dissimilar new experiences”. The paper then interestingly links schema theory and the “quality without a name”: if a schema is “whole”, as a gestalt, then it is of quality, quality without a name, which “is a synonym for wholeness in the pattern concept summary”.
Then, the paper defines/describes schema, introducing the ideas of variables, which can take constrained range of values. Specific configurations of some variables values imply some values, further constrained values of other variables, in a kind of (positive or negative) feedback loop. It also introduces relations among schema: has-a/part-of relations and is-a relations and describes how memory builds schema, when solving a problem the first time, or how memory retrieves/uses schema when facing a recurring situation. It emphasises that schema are acquired/refined “either by learning, by doing, or [by] studying illustrating examples”. This last point is interesting with respect to the documented patterns and also teaching patterns!