[Sigia-l] facet vs. term vs. concept (was Re: Faceted Classification)

[karl fast]

> "World Trade Center" and "Twin Towers" were, until recently, equally
> popular terms for the buildings that used to define the NYC skyline.
> Neither is a misspelling of the other, and the more popular of the two
> may not have been the desired term. Without a controlled vocabulary,
> there would be these two facets with the same content.

I think you're confusing 'facet' with 'term' and 'concept.' 

A thesaurus is a map of various concepts.

These concepts are represented by terms (ie: words and phrases). If
a concept can be represented by multiple terms you choose a
preferred term and establish USE/USE FOR relationships.

Facets are principles of division used to organize the concepts. A
facet *may* be represented by a term, but it doesn't have to be


  Note: people use different terminologies. The XFML.org spec seems
        to define facets as the top level divisions only. And it
        talks about 'topics' instead of 'terms' (it says "the things
        within facets are called topics"). I was taught to think
        about facets as any principle of division within the CV.
        Argue amongst yourselves over the merits of this.


To use your example:

  "World Trade Center" and "Twin Towers" are terms that represent
  the same concept. The controlled vocabulary defines which term is
  preferred for representing the concept.

  The facets are used to organize these concepts into hierarchies of
  mutually exclusive concepts.

  Suppose we have this:

     <big things that no longer exist>
           World Trade Center
           Lighthouse at Alexandria
           Tower of Babel     

  Here our facet is <big buildings...> but it's used only as an
  organizing principle. "World Trade Center" is a _term_ within that
  facet that represents the _concept_ of that building. Presumably
  we have established a USE/USE FOR relationship with "Twin Towers."
           
  But we could also have this:
  
      skyscrapers
          World Trade Center
          Empire State Building
          Petronas Towers
          Sears Tower         

  Here the facet is 'skyscrapers.' It is used not only as a
  principle of division, but also as an indexable term.


Here's another example from the Art & Architecture thesaurus.

  - <Weapons and ammunition> is a facet, but not a term. It exists
     strictly as a principle of division.

  - The concepts in the main facet are represented by their own
    terms. And we can see from the hierarchy that they're facets in
    their own right (a standard trick in the AAT).
    
  - <explosive weapons> is a facet, but it's not indexable.  

  - bombs is a facet because it helps distinguish between different
    types of explosive weapons, and it's also an indexable term.

  
<Weapons and ammunition>
   weapons
       ceremonial weapons
       combination weapons
       edged weapons
       <explosive weapons>
            bombs
                aerial bombs
                depth bombs
                nuclear bombs
            grenades
                antipersonal grenades
                antitank grenades
                ....               
            ....
       incendiary weapons
       <percussive weapons>       
       ....
    ammunition
       shot (ammunition)
       shrapnel
       <ammunition for artillery>
            bar shot
            canister shot
            ....
        <ammunition for small arms>
            blank cartridges
            caseless cartridges
            ...


You can explore this branch of the thesaurus here:
            
http://vocab.pub.getty.edu/cgi-bin/aat_browser/aat_hier.pl?F^V.TK^keywords=weapons+ammunition&searchtype=term&file=index.html


       

--karl