Hi Russ,
Thanks for your input and link to an earlier presentation of yours.
Agree that the proposal only applies to group hierarchies, i.e., to
groups representable by the Common Data Model 2/extended/enhanced
which for practical purposes means groups exposed by the netCDF4 API.
Your way of putting it is better because it's more generic: we only
seek to define metadata inheritance for hierarchical groups, no matter
the external representation of the group.
Cheers,
cz
Le 16/09/2013 12:06, Russ Rew a ?crit :
>> Dear all,
>
> I'm also glad to see this discussion surface. Since I first presented
> "Developing Conventions for netCDF-4" at the 2007 GO-ESSP meeting:
>
> http://www.unidata.ucar.edu/presentations/Rew/nc4-conventions.pdf
>
> I've been hoping that netCDF-4 feature adoption would begin to gain
> traction in the community (see slides 19 and 20 of this 2010
> presentation for my "chicken-and-egg logjam" illustration):
>
> http://www.unidata.ucar.edu/presentations/Rew/agu_2010_nc4_Rew.pdf
>
> I like the Zender-Habermann-Leonard (ZHL?) proposal for Group
> Attributes, but would like to point out a potential problem for its use
> with HDF Groups: they aren't actually hierarchical. In HDF5, Group A
> can be a parent of Group B, which in turn can be a parent of Group A,
> forming a cycle instead of a hierarchy. The graph of the Group-subGroup
> relation in HDF5 can form an arbitrary directed cyclic graph, though
> this is not permitted in netCDF-4, in which only Group *hierarchies* can
> be created through the netCDF-4 API.
>
> Without a restriction to hierarchies, attribute inheritance is not
> useful, which is why we required group hierarchies for dimension
> inheritance in netCDF-4. So I think the proposal should include a
> restriction to only hierarchical Group structures, which also has the
> desirable property that each Group, except for the root, has a unique
> parent Group.
>
> --Russ
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(
Received on Mon Sep 16 2013 - 23:26:53 BST
