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#104: Clarify the interpretation of scalar coordinate variables
-----------------------------+----------------------------------------------
  Reporter:  jonathan        |       Owner:  [email protected]
      Type:  defect          |      Status:  new                          
  Priority:  medium          |   Milestone:                               
 Component:  cf-conventions  |     Version:                               
Resolution:                  |    Keywords:                               
-----------------------------+----------------------------------------------
Comment (by stevehankin):

 What CF calls a "scalar coordinate variable" is syntactically an
 "auxiliary coordinate" i.e. it lacks the axname(axname) syntax, and it is
 associated with a variable via the coordinates attribute.  About
 "auxiliary coordinate variables" CF says

 {{{
 The use of coordinate variables is required whenever they are applicable.
 That is, auxiliary coordinate variables may not be used as the only way to
 identify latitude and longitude coordinates that could be identified using
 coordinate variables.
 }}}

 So for length >1 coordinates CF '''insists''' on using the axname(axname)
 syntax.  but for length=1 coordinates CF allows us to borrow the auxiliary
 coordinate syntax.  Through these 2 rules CF has orphaned the concept of a
 "scalar auxiliary coordinate variable".  This missing concept lies at the
 heart of the current discussion.

 This is a genuine flaw in the current CF specification.  It deserves to be
 fixed.  The text at the start of this trac ticket is wrong when it says
 that it is not proposing a ''material change''.  But it is a needed
 change.

 The text, however, deserves to be expanded to much better illuminate the
 nature of the problem that it is fixing.  Frankly, it should get explicit
 in saying that it is defining a rule that addresses an ambiguity created
 by the definitions of ''auxiliary coordinate variable'' and ''scalar
 coordinate variable''.

-- 
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/104#comment:15>
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