Defining My Terms

`Now you talk like a reasonable child,' said Humpty Dumpty, looking very much pleased. `I meant by "impenetrability" that we've had enough of that subject, and it would be just as well if you'd mention what you mean to do next, as I suppose you don't mean to stop here all the rest of your life.'
`That's a great deal to make one word mean,' Alice said in a thoughtful tone.
`When I make a word do a lot of work like that,' said Humpty Dumpty, `I always pay it extra.'
--Lewis Carroll, Through the Looking Glass

It seems that most language used in describing Internet concepts, especially around ontology and other structured data, are repurposed from other disciplines. (As words get repurposed, so do ideas. The only difference is that we pretend that these are unique and pioneering ideas, rather than acknowledge that we are standing on the shoulders of giants.)

The following are the terms I use a lot, and and how I currently define them to myself. As this experimental self-education continues, I plan to update these definitions as needed.

Ontology - An ontology is a set of concepts and their relationships to each other. The most important aspect of an ontology is those relationships. They give it meaning. Ontologists come in two stripes: those who create ontologies for practical use (that's me!) and those who spend time with the theoretical aspects of ontology. These ontologists wrestle with the problem of defining a semantic relationship to a computer. To do that, your own mind must be very clear on what that relationship is. What is a synonym? What is a related concept, and how does that relationship differ from an alternate parent concept?

Taxonomy - Often used interchangably with Ontology, a taxonomy is a hierarchical category structure in which concepts have one true place. It is more authoritarian and less flexible than an ontology. The Yahoo! directory category structure is a taxonomy by this definition.

Controlled Vocabulary or Thesaurus - (not Roget's thesaurus) These are synonym lists. They point out alternate spellings or words for the same concept. These are of great use in allowing users to perform conceptual searches without exhaustive Boolean logic. Google's misspelling helper is an example of a synonym list, as is the Library of Congress Subject Headings.

Faceted Classification - Every item, idea, or person has multiple attributes that are not mutually exclusive. Things have color and size, for instance. If you gather information (metadata) on these various facets, you can allow searchers to choose the facets they find most important. EBay uses facets in its Product Finders, which can be combined with category browsing. This allows a very targeted search using seller-provided metadata.