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Book review: Darwinia
Reviewed: Friday, August 11, 2006

Summer reading: Spin
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Classification and Categorization: a difference that makes a difference
Elin K. Jacob, 0 , (Paper URL)
Thursday, March 10, 2005

Each discipline learns its own lingo and style. Sometimes it's hard to see the substance for the style - after all, isn't form supposed to follow function? That's how I felt when I first started reading this paper by Elin K. Jacob. What are all these words doing here! My philosophy and liberal arts background stood me in good stead, however, and things started to flow again after a few of pages. I was glad I persevered because the paper does make several useful points.

The paper cause d'etre is the current foment in Library Sciences and Philosophy regarding information and our relationship with it. It's a discussion that drives pure engineers batty - let's just build the thing already - but that is foundational to getting things right in the long run. As people like Foucault pointed out, architectures (whether of buildings or systems) change the people that inhabit them; power and control exist even when there is no guiding hand. It behooves us therefore to think about what we create; especially about the long term effects of the relationships that our systems support and enable.

Elin's goal is to untangle and taxonimize the differences between categorization and classification and then to use the taxonomy to create better human / machine systems. To summarize, Elin defines categorization as dividing the world into groups of perceptually similar entities - note that the metric used is context dependent and shifting (cf. Barsalou and others). Classification, on the other hand, refers to grouping things based on some predefined systems in an "orderly and systematic assignment of each entity to one and only one class within a system of mutually exclusive and nonoverlapping classes." (emphasis mine). Categorization creates new relationships; classification exploits existing ones (it is defining).

As an aside, Elin points out the parallel between some basic assumptions of knowledge classification ("universal order, unity of knowledge, similarity of class members, and intrinsic essence") and the classical theory of categories (essential features, hierarchical structure, category definition viewed as a summary) but doesn't explore in depth how the toppling of classical category theory by Wittgenstein and Rosch has altered views in knowledge classification.

The paper goes on to discus how the mechanisms of classification and categorization differ in their attempts to establish order in the world. To summarize very roughly: classification is rigorous and fixed (you're not really "allowed" to alter the classes once you start); the structures (usually hierarchical) produced form powerful external scaffolding that minimizes cognitive load. Categorization is fluid and variable; the frameworks produced are often ephemeral. It is categorization, however, the exhibits true creativity in the never-ending play of flexible and dynamic relationship. Classification is knowledge bearing: knowing an entity's class tells me much about it because the class exists as part of a fixed structure; knowing an entity's category may not tell me much of anything at all because categorization is extremely context dependent...

The two techniques complement each other; This is from the paper's conclusion:

... the strength of classification is its ability to establish relationships ... that are stable and meaningful. But the rigidity of structure that supports these relationships has its corresponding disadvantages. In particular, traditional classification systems are context-independent: ... these systems [can] severely constrain the individual's ability to communicate with the system in a meaningful and productive manner. In contrast, systems of categorization ... are highly responsive to ... the immediate context. ... But the responsiveness and flexibility of the ... system effectively prohibit the establishment of meaningful relationships because categories are created by the individual, not the system, and are thus fleeting and ephemeral.

What we need, I think, is a theory of how to move smoothly from categorization to classification. We do this constantly already but not necessarily as well as we could or as well as we need to as the information flux of our environment continues to increase.

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Copyright -- Gary Warren King, 2004 - 2006