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 écrit : >> 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 > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > -- Charlie Zender, Earth System Sci. & Computer Sci. University of California, Irvine 949-891-2429 )'( _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
