Re: Options for Groups in netCDF-4

Russ,

A few comments.

1. General Intro

First, I wanted to suggest a general comment that might be in
the introduction.

The HDF5 Group object is used to create a structured name space
for a file. HDF5 provides a very generic mechanism, with very little restriction on how it can be used.

If NetCDF4 uses Groups, it will define a profile (or profiles)
to specify how HDF5 Groups (and names) are used and interpreted
within NetCDF4.  This document presents ideas for what the
profile should be.

2. RE HDF5 names

HDF5 places very little restriction on path names.  NetCDF4
should certainly define restrictions as needed.

3. Should there be more than one profile?

This document presents several plausible approaches to using
HDF5 Groups and names.

Is it necessary to select only one? Or is it worth considering
the possibility of multiple profiles (with the NetCDF4 software
managing the differences.)

From the initial document, I see several potential profiles:

 * netCDF3 compatibity
 * "multifile" file, e.g., Group == netCDF3 file
   - distinguished netCDF root
* Hierarchical NetCDF - restricted to a tree - general graph allowed
 * several possible profiles for using/interpreting path names
 One approach would be to define several profiles, with format
support to indicate what profile to use and mappings between profiles, if necessary (e.g., for netCDF3 compatibility it
is necessary to define how to interpret paths as names).

The reason for considering this approach is that it would
be a shame to lock in one model now, only to discover that
users need something else in a few years.  A multiple
profile approach can be extended with new profiles in
the future.