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Hi John, Thanks for taking the time to come up with this specification. It looks like a good start. I do have some concerns about the complexity of the spec, though, and would like to suggest a few changes that might make it easier to use. I believe that this spec is too complicated for most potential users. For instance, it appears that any software that is able to read these collections will have to have parse a SQL-like expression in order to interpret a collection. Another source of complexity is the varying dimensionality of the dimensions and observations (either 1D or 2D depending on the type of data). Still another example is the use of character variables for storing attribute data for collections (should software assume that any character variable is an attribute)? It's also difficult to edit data with this convention. How would I remove an individual profile from a collection? Or, worse, what if points needed to be added or removed from an individual profile? I'd have to regenerate the entire netCDF file in the latter case. That makes this convention only practical as an archive format. An alternative would be to store each individual profile/trajectory/time series in a separate netCDF file. Collections would consist of a set of netCDF files stored in a zip or jar file. The zip file could also contain some sort of (XML?) manifest file that could contain metadata about the collection as a whole. Any metadata associated with an individual profile would be stored as a global attribute in the appropriate netCDF file. Editing a profile would be as simple as extracting the netCDF file from the archive, rewriting it, and then storing it back in the jar file. To make it even easier for consumers of this data, I would alsorestrict the data type of all variables to double. Also, all four x,y,z,t coordinates
would be required. Some examples (from your CDL examples): Collection of point data ------------------------ Unchanged (just one file in archive) Collection of profile data -------------------------- For each netCDF file: variables; double lon(1); double lat(1); double z(obs); double time(1); double humidity(obs); double temperature(obs); double pressure(obs); Collection of trajectories -------------------------- For each netCDF file: variables; double lon(obs); double lat(obs); double z(obs); double time(obs); double humidity(obs); double temperature(obs); double pressure(obs); Station time series ------------------- variables; double lon(1); double lat(1); double z(1); double time(obs); double temperature(obs);