DeleteMe after 2006-10-08 -- Moved to CategorizationModels
------
I couldn't find any wiki pages on general classification techniques, so I created one. (There is a topic called "CategoryTheory", but it's name overlaps with the wiki category framework system, so it gets lost in the shuffle.) [Oops: found CategorizationModels. Guess I gotta work on a merge]

Classification is a way to identify items so that they are easier to find and easier to relate to each other. Here are some of the common techniques:

* Hierarchies
** Pro: Intuitive
** Con: Don't deal with orthogonal traits well. See LimitsOfHierarchies

* See-also lists
** Pro: Intuitive
** Con: Require too much effort to update

* Sets
** Pro: Flexible
** Con: Not inherently intuitive, difficult to inspect

* Weighted Sets
** Pro:
** Con:

The Cadillac[1] of classification systems in my opinion would be a combination of weighted sets and weighted see-also's. For example, for any item to be classified, one could create a list of weighted categories and weighted see-also's. Example:

  Item: "Perkins Lab Coat #6"

  Categories
  -----------
  Medical Supplies: 1.0
  Scientific Supplies: 1.0
  Clothing: 0.8
  Safety Equipment: 0.4
  Halloween Supplies: 0.3

  See Also:
  --------------
  JVM medical washing machine: 0.9
  Perkins all-in-one surgery kit: 0.6


Weights are assumed to be zero to one. In practice, this could be implemented with a RDBMS using two many-to-many tables with weights.  

[1] AmericanCulturalAssumption: "Cadillac" used to be the most expensive car. Imports generally have taken over this niche, but the phrase has remained.

--top
----
CategoryClassification