@davidhassell commented on this pull request.
> + +A data variable defines its domain via its own attributes, but a +domain variable provides the description of a domain in the absence of +any data values. It is of arbitrary type since it contains no data. It +acts as a container for the attributes that define the domain. The +purpose of a domain variable is to provide domain information to +applications that have no need of data values at the domain's +locations, thus removing any ambiguity when retrieving a domain from a +dataset. Ancillary variables and cell methods are not part of the +domain, because they are only defined in relation to data values. + +The domain variable supports the same attributes as are allowed on a +data variable for describing a domain, with exactly the same meanings +and syntaxes, as described in <<attribute-appendix>>. If an attribute +is needed by a particular data variable to describe its domain, then +that attribute would also be needed by the equivalent domain variable. I appreciate your concern, here. I feel that the approach is guaranteed to work for as long as CF still insists that a data variable encodes is own, implicit domain, which is to say for the foreseeable future. My one point of concern, however, is for a scalar data variable that innocently has the `dimensions` attribute - how can we tell if it is a data variable or a domain variable? Perhaps using the `dimensions` attribute as the identifying feature could be replaced by the existing `cf_role` attribute. I think that this could be a bit safer: ``` char domain ; domain:cf_role = "domain" ; domain:dimensions = "x y" ; domain:coordinates = "lat lon" ; -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/pull/302#discussion_r493637227 This list forwards relevant notifications from Github. It is distinct from cf-metad...@cgd.ucar.edu, although if you do nothing, a subscription to the UCAR list will result in a subscription to this list. To unsubscribe from this list only, send a message to cf-metadata-unsubscribe-requ...@listserv.llnl.gov.