FACET - What it Means

Common senses from which the technical ones below (#1-#4) try to borrow

"Facet" is not widely used as a technical term.  (DMOZ ignores it).  But these may be interesting.
 
[0a] - http://dictionary.reference.com/search?q=facet
          Various reference sources

[0b] - http://thesaurus.reference.com/search?q=facet
         Roget's, in a very old edition

[0c] - http://www.wordsmyth.net/live/home.php?script=search&matchent=facet&matchtype=exact
         Bob Parks' combined reference

Sense 1 - Scripts associated with a data type which can manage its constraints and defaults

This is the oldest technical sense - came in late '70's as a way to model Minsky's Frames.  Facets were originally processes (in Lisp, Smalltalk, or Simula) which (on request) checked constraints or computed default values.

[1a] -http://www.cs.umbc.edu/771/current/presentations/frames.pdf
         FRL, KRL, KL-ONE, LOOPS, KEE; example facets shown in KIF.  Historical references cited
                  
[1b] - http://www.ndsu.nodak.edu/instruct/juell/cs724s03/foils/frl.html
          Overview containing links to original FRL def by Goldstein & Roberts

[2a] - http://www.lexikos.com/words/scripted.jsp
          Similar version now being implemented for topic maps.  Uses WORDS scripts as processes

[2b] - http://www.lexikos.com/psi/words/aspect/
          PSIs for occurrence types of the (slot-like) aspects holding such (facet-like) processes. 

Sense 2 - Features that characterize a numeric data type, including value constraints

This replaces the procedures of sense 1 with a list of primitive data features that constrain values sufficiently to let application code check them.  Default values seem forgotten in XSD, which barely touches on sense 3 (see 5d).

[3a] - http://www.w3.org/TR/xmlschema-2/#facets
          XSD definitions of related typing.  Data only.  The programs are kept separate

[3b] - http://edocs.bea.com/wli/docs70/classdocs/com/bea/web/validation/FloatWord.html
          Example of such a program from the BEA application server world

[4a] - http://www.altheim.com/ceryle/api/org/ceryle/tm/Facet.html
          Larger set for Topic Maps, based on TM4J and PSIs.  Includes code for fixed defaults
 
[4b] -  http://www.infoloom.com/pipermail/topicmapmail/2003q4/005440.html
           A string for such a value OR a constraint on one.  Next message gives examples

Sense 3 - Features that characterize enumerated data types, including classification trees

In any formal language, enumerated types differ from scalar types and need different treatment.  Options with no associated order define  sets.  Imposing a hierarchy on them creates an FC tree, which can degenerate into a comparative series.
 
[5a] - http://www.kmconnection.com/DOC100100.htm
          Top homepage from Google for "faceted classification" - gives library science links

[5b] - http://www.poorbuthappy.com/fcd/
          An active mailing list for users of the FC type of data
 
[5c] - http://xfml.org/
          An exchange format for FCs based on TMs, seeking compatibility with RDF, and RSS
 
[5d] - http://www.w3.org/TR/xmlschema-2/#rf-enumeration
          XSD explicitly excludes "entity" order - so it just does sets - no trees or series

[6a] - http://www.topicmapcentral.com/wiki/Wiki.jsp?page=FacetedClassificationPattern
          Kal's published design pattern for building FC hierarchy out of topics and associations

[6b] - http://www.lexikos.com/psi/psitree.jsp
          Dan's pattern for building a static FC hierarchy from PSIs and anchor strings

[6c] - http://www.infoloom.com/pipermail/topicmapmail/2003q4/005432.html
          Carlos' observation that FC might best be kept peripheral to Topic Maps

Sense 4 - The original meaning in HyTime, and its comparison to RDF

When I Googled "facet RDF",  I got very little back of interest except from Topic Map people, whom I suspect are the only ones seeing the comparison.  We have since officially dropped related specs, so this sense is best labeled archaic, obsolete, and dead

[7a] - http://www.w3c.rl.ac.uk/SWAD/deliverables/8.1.html
          Top spec-like hit in Google from the RDF world.  It seems similar to sense 3

[7b] - http://www.isotopicmaps.org/pipermail/sc34wg3/2003-April/001631.html
          This was good for background; and it starts a thread examining this sense some


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