Classification

While the terms classification and categorization are often used interchangeably in casual conversation, they represent two distinct approaches to organizing information.  The easiest way to distinguish classification and categorization is by their level of formality and structure: classification is formal, systematic, and rule-based, while categorization is informal, intuitive, and based on similarity.

Classification is the process of assigning important things in an area of knowledge to a set of pre-defined, mutually exclusive category or class based on strict rules or criteria. Classification relates to the inclusion of a thing in a set.  It is typically a top-down approach designed for objectivity and consistency.

Things tend to be classified into three broad hierarchal categories to help make distinctions clear:

• Basic level category is the most salient things; the differences between categories is the most noticeable, prominent, and important
• Superordinate level categories are above the basic level in hierarchy and tend to have a high degree of generality and tend to be more abstract than things in the basic level
• Subordinate level categories are below the basic level in hierarchy and tend to be more specific or are less general and have clearly identifiable and highly detailed individuating and specific features

The Greek philosopher Aristotle (384-322 B.C.) first came up with the idea of classifying plants and animals by type, essentially creating the notion of a hierarchy or taxonomy.  The idea was to group types of plants and animals according to their similarities thus forming something that looked like a "tree" with which most people are familiar.

Classification is about organizing knowledge.  The only thing better than classifications is standard classifications.  One well known classification system is the Dewey Decimal Classification used by libraries. Imagine what it would be like if every different library had a different classification system for organizing its books.

A taxonomy is a formal tree-like hierarchal structure that organizes things into a strict, hierarchy based on its classification.  In a taxonomy, classification is linear and top-down. Every child node has a direct, explicit relationship to its parent node, and the structure is primarily used to group similar items together. By contrast an ontology is a graph-like structure which describes all  the ways a thing interact with other things in an area of knowledge.

Taxonomies and ontologies are both tools for organizing knowledge. Taxonomies and ontologies are different approaches to represent different aspects of knowledge in machine readable set of knowledge.

Artificial intelligence is about bringing taxonomies and ontologies to life. What that means to me is that if you have an artificial intelligence software application, but you have no machine readable taxonomy or ontology for the AI to use; what you get will not be that interesting.  But, if you have both artificial intelligence software and a taxonomy or ontology, magical things can be the result.

Here is an example of the classifications in a small financial reporting scheme:

XBRL International publishes arcroles (higher level classification capabilities) that can be used to represent different types of associations in a standard Link Role Registry.  Included in that registry are arcroles related to accounting and financial reporting.

An excellent book that discusses classification is Everything is Miscellaneous by David Weinberger. (Here is a preview.) The book points out that there are three orders of order:

1. First order of order. Putting books on shelves is an example the first order of order.
2. Second order of order. Creating a list of books on the shelves you have is an example of second order of order. This can be done on paper or it can be done in a database.
3. Third order of order. Adding even more information to information is an example of third order of order. Using the book example, classifying books by genre, best sellers, featured books, bargain books, books which one of your friends has read; basically there are countless ways to organize something.

Weinberger points out in his book that the third order of order removes the limitations which people seem to assume exist when it comes to organizing information. Weinberger says this about the third order of order:

"In fact, the third-order practices that make a company's existing assets more profitable, increase customer loyalty, and seriously reduce costs are the Trojan horse of the information age. As we all get used to them, third-order practices undermine some of our most deeply ingrained ways of thinking about the world and our knowledge of it."

Weinberger's book points out two important things:

1. That every classification scheme ever devised inherently reflects the biases of those that constructed the classification system.
2. The role metadata plays in allowing you to create your own custom classification system so you can have the view of something that you want.

Additional Information:

• Professional Oriented Knowledge Framework
• The Discipline of Organizing
• Taxonomies, All the Way Down
• Levels of Categorization