> 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
Received on Mon Sep 16 2013 - 13:06:00 BST
