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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 rhattersley):

 Consider a CF-netCDF compliant file containing a single data variable. It
 is perfectly compliant to define both a global "comment" attribute and a
 data variable "comment" attribute containing different information. It's a
 worrying consequence of the all-attributes-are-really-data-attributes
 approach that it renders the global attribute meaningless.

 Replying to [comment:78 davidhassell]:
 > Remember that one of the aims of the data model is to set the groundwork
 to expand CF beyond netCDF files.

 Whilst this is true, it's also important to remember that the terms of
 reference for the CF 1.5 data model constrain us to be consistent with
 version 1.5 of the CF-netCDF conventions.

 In particular, the statement "When an attribute appears both globally and
 as a variable attribute, the variable's version has precedence" has been
 shown to be subject to two different interpretations. Since we cannot go
 back in time and re-write version 1.5 of the conventions (but we should
 clarify the next version!) we must embrace this ambiguity in the data
 model, and the data model needs to contain both the global and variable
 attribute concepts.

 FWIW, the title of section 2.6.2, "Description of file contents" suggests
 that the original authors saw these attributes as file-based as opposed to
 variable-based.

 Regards,
 Richard

-- 
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/95#comment:79>
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