Options for Groups in netCDF-4

Hi,

I've begun to think about whether we should make use of HDF5 Groups in
netCDF-4, and if so how we should make use of them.  I don't have any
recommendations yet, but here's a short discussion of some of the
issues:

  http://my.unidata.ucar.edu/content/staff/russ/groups-rfc.html

This is a request for comments on the above draft.  I'm leaning
towards using HDF5 Groups, but haven't decided which of the two models
described in the above draft to recommend.

--Russ