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#79: Handling and formatting of vector quantities in CF
-----------------------------+----------------------------------------------
  Reporter:  lavergne        |       Owner:  [email protected]
      Type:  enhancement     |      Status:  reopened                     
  Priority:  medium          |   Milestone:                               
 Component:  cf-conventions  |     Version:                               
Resolution:                  |    Keywords:  vector                       
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Comment (by markh):

 Replying to [comment:56 pbentley]:

 Hi Phil

 > (In which case it might also be useful to debate whether or not there is
 value in identifying a new CF `featureType` of `vector` to reinforce the
 intent.)

 I'm not sure that a new feature type definition is helpful here.  These
 containers may be used for different feature types, a structured grid may
 define a vector as may a trajectory or a time series, I think the concepts
 are independent.

 > I wonder, perhaps, if 'umbrella name/variable' is not really the right
 terminology here. Taken in isolation, the attribute `umbrella_name`
 suggests that its value is providing the name of an umbrella! Which
 clearly is not the intention ;-) I suspect that what you were wanting here
 is `umbrella_variable_name` or `umbrella_quantity_name`?

 > Personally, however, I'd prefer that the term 'umbrella' was dropped.
 Within the geoinformatics realm I think there are more commonly used terms
 which more accurately define the role being played by 'umbrella variable'.
 For example: parent, container, composite or aggregate (no doubt there are
 others).

 I like the term container here, it seems quite intuitive to me; a marked
 improvement on umbrella.

 > Alternatively, rather than targeting a (hazily-defined?) generic use-
 case, one could target the specific use-case suggested by the title of
 this ticket (i.e. vector quantities). Thus, one might have, say,
 `vector_quantity_name` in place of `umbrella_name`.

 I think that the aim of this ticket should be to deliver the specific use
 case of vector quantities.  That said I think it is worth keeping an eye
 on the future and other uses for a container/umbrella so I think vector
 should be the first of a potential number of types, with scope for
 extension, not treated in complete isolation. Hence I propose the generic
 type and one explicit instance of that type.

 Perhaps we could define the following to deliver to the scope of this
 ticket.

  * Container variable
   * a new type of CF variable
  * container_type
   * an attribute on a Container variable
   * a controlled vocabulary within CF, defined in the specification
   * initially the only valid value is:
    * vector
   * the container type then defines a list of further container attributes
 for that type (as above)
  * container_name
   * an attribute on a Container variable
   * a controlled vocabulary within CF, maintained as a list like
 standard_names
   * the container_name would be linked to a valid container type, e.g.:
    * container_name: "sea_ice_displacement", type: "vector"

 what do you think?

 mark

-- 
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/79#comment:57>
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