Hi Nan I think I understand you approach, it seems logical and helpful to me.
It feels like all your examples are in my category b: > b. reference a subset of the file dimensions referenced by the data variable > with the ancillary_variables attribute and thus relate to the data variable in the same way auxiliary_coordinates do, just with different inferred semantics. many thanks for the feedback mark -----Original Message----- From: CF-metadata on behalf of Nan Galbraith Sent: Wed 13/02/2013 19:55 To: cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] Ancillary Data I use a singleton variable to record the magnetic correction that's been applied to my wind and/or current variables; it's dim(1) and is listed as an ancillary to any variables that have been affected by the rotation. It could be an attribute of each of those variables, but making it a free-standing variable lets me give it units and attributes. That's important because I record the model name and version date, the URL of the NGDC calculator site, the inputs to the model (date and location for which the calculation was done) and the estimated rate of change. Maybe this is just a technicality - but I also use an empty 'container' variable for instruments, which has ancillary variables with a depth dimension for manufacturer, model, serial number, and reference URL. The instrument variable is tied to 'obs data' variables via NODC's 'instrument' attribute, but has no dimensions of its own; the individual component variables (like serial number) have a dimension that matches the depth dimension of the obs data variables. - Nan On 2/13/13 12:15 PM, Hedley, Mark wrote: > Hello CF community > > I have been perusing the CF conventions again, particularly the section on > Ancillary Data > http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html > > The conventions make the statement: > > The nature of the relationship between variables associated via > ancillary_variables must be determined by other attributes. > > The example given provides data variables which reference the same dimensions > in the file: thus they data arrays are the same size. However, the > conventions do not seem to mandate this. > > I am interested in the use of the > ancillary_variables > attribute in real world datasets. > > Do people have examples they can share of ancillary datasets which: > > a. reference the same file dimensions as the data variable with the > ancillary_variables attribute references > > b. reference a subset of the file dimensions referenced by the data > variable with the ancillary_variables attribute > > c. reference file dimensions which are not referenced by the data variable > with the ancillary_variables attribute > > I am particularly interested in examples of case c, as I feel this is > markedly different from cases a and b and requires a different kind of > support if it is in use. > > many thanks > mark > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > -- ******************************************************* * Nan Galbraith Information Systems Specialist * * Upper Ocean Processes Group Mail Stop 29 * * Woods Hole Oceanographic Institution * * Woods Hole, MA 02543 (508) 289-2444 * ******************************************************* _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
