>I agree with your reasoning. It is worth considering the use of Groups, but >the approach should be weighed against the best proposals that can be >generated that stick to the classic model. Fundamentally the need is for 2 >bit of semantics: > > 1. associate components together so they form a conceptual N-vector object > 2. associate metadata with the N-vector object
Having these two bits of semantics would be really valuable because it also provides a generic method for handling tabular data within netcdf, which is something I think we need. If you want to represent a set of events (e.g., earthquakes) in netcdf, I believe the best way to do it is to have a bunch of variables (e.g., time, lat, lon, magnitude) with a common "ID" dimension. Having a common dimension links them together implicitly, but there's currently no good way to say explicitly "these variables are different features of this set of entities" or to provide metadata about the collection, like "this is a catalog of Japanese earthquakes of magnitude 5.0 and greater". Something simple along the lines of the coordinates attribute would probably suffice. I'm not sure whether it would be better to attach it to the ID dimension, and use that as the holding point for metadata associated with the table, or whether it would be preferable to simply have a dummy variable, as is used for map_projection metadata. (I had more conclusions about some of these issues, but lost the document where I collected all my thoughts in a hard-drive crash...) This would also provide a stepping-stone to better handling of spatial categorical data. Currently, CF says to use flag_values and flag_meanings for categorical data, but that gets really awkward and human-unfriendly if you have more than a handful of categories. It would be much more elegant to have the meanings of the numeric values defined by reference to a table. (This also solves an issue I posted about a while back: we could have one set of standard names for use with controlled vocabularies like the Area Type and Region Names tables, and another for user-provided categorizations, which would then be enumerated in the same file.) Cheers, --Seth _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
