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#95: Development of CF 1.5 Data Model
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  Reporter:  markh           |       Owner:  [email protected]
      Type:  task            |      Status:  new                          
  Priority:  medium          |   Milestone:                               
 Component:  cf-conventions  |     Version:                               
Resolution:                  |    Keywords:                               
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Comment (by markh):

 Replying to [comment:48 davidhassell]:

 Hello David

 I am struggling more with the proposal of an unordered collection of
 !DomainAxis instances than i have with an ordered one.  I thought one of
 the objectives was to define the Field's data array, without domain axis
 ordering this seems not to be delivered.

 I think if we are to define the !DomainAxis construct the Field must
 define an ordered list of them as its domain_axes.

 The instance of a Field from my example which you have described does not
 deliver on some key aspects I require, I will try to explain how:

  * the ordering of the dimensions defined by the height_level and time
 coordinates is not defined;
   * my Fields will become extensive in height_level and time, during
 aggregation; how would my ggregator know which way round to order these
 dimensions in the data array?
  * you have defined forecast_period and forecast_reference_time as
 functions of t, suggesting a link to the time coordinate.
   * one of these two coordiantes is independent of time, while the other
 is a function of both time and the previously mentioned coordinate
 independent of time.
    * which is which is either decided by inspection of the data during
 aggregation or by user preference stated to the aggregator
  * you have defined source and institute as functions of the domain_axis
 defined by an ensemble_member coordinate:
   * this is explicitly not the case, these coordinates are not stated to
 vary with any other coordinates

 Does your interpretation of the model allow for a coordinate which has
 only 1 data value and is not a function of any !DomainAxis?

 Also, when comparing Fields:
  * do the domain axis identifiers form part of the comparison criteria?
  * do the domain axes a coordinate is a function of form part of the
 comparison criteria?

 thank you
 mark

-- 
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/95#comment:49>
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