#173: clarify the dimensions of ancillary variables
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 Reporter:  jonathan        |      Owner:  cf-conventions@…
     Type:  defect          |     Status:  new
 Priority:  medium          |  Milestone:
Component:  cf-conventions  |    Version:
 Keywords:                  |
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 The purpose of ancillary variables (Section 3.4 of the convention) is to
 provide metadata about individual values in data variables. Given this
 purpose, I believe that an ancillary data variable should not have any
 dimensions which its data variable does not have. To clarify this, I
 propose that the following should be appended to the first paragraph of
 Section 3.4: "The dimensions of an ancillary variable should be the same
 as or a subset of the dimensions of the data variable with which it is
 associated by the `ancillary_variables` attribute, but the order of the
 dimensions is not restricted." This text corresponds to a similar sentence
 in Section 7.2 about cell measures variables.

 I'm proposing this as a defect ticket because this is my understanding of
 what the convention intends. Please comment if you don't think so. Thanks.

 Jonathan

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Ticket URL: <https://cf-trac.llnl.gov/trac/ticket/173>
CF Metadata <http://cf-convention.github.io/>
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