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[netCDF #EEP-446216]: Reading of HDF5 files with NetCDF 4.1.1

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  • Subject: [netCDF #EEP-446216]: Reading of HDF5 files with NetCDF 4.1.1
  • Date: Wed, 12 May 2010 09:02:42 -0600
Hi Thomas,

> I have a question regarding the reading of HDF5 files, that are NOT created 
> with NetCDF:
> 
> In the documentation I found that
> "The HDF5 files created by netCDF-4 will be readable (and writable) by any 
> HDF5 application. However, netCDF-4.0 cannot read any HDF5 file, only those 
> created by netCDF-4."

That was true for the 4.0 release, but later releases have additional support 
for
reading some HDF5 files that were not created by the netCDF API.  A recent list 
of 
what HDF5 features would make it unreadable through the netCDF-4 API is here:

  http://www.unidata.ucar.edu/netcdf/docs/faq.html#fv15

and also referenced here:

  http://www.unidata.ucar.edu/netcdf/docs/faq.html#fv20

> In the release notes from the version 4.1.1 I found:
> "Support for reading some existing HDF4/HDF5 data archives using the netCDF 
> C/Fortran APIs."
> 
> So my questions:
> 
> Is it possible to read HDF5 files which are NOT created by the NetCDF library 
> (e.g. created with the HDF 5 library) and what does the qualifier "some 
> existing" mean in the sentence in the release notes mean? Is there a list of 
> possible limitations when reading the NetCDF files or do only the limitations 
> listed in the chapter "4.11 Interoperability with HDF5" in the documentation 
> apply?

We have to update some of the documentation to accurately describe what HDF5 
files
can be read by the latest 4.1.1 release.  For example, as you have pointed out, 
the
section "4.11 Interoperability with HDF5" is clearly out of date, as it refers 
to 
HDF5 1.8 not yet being available and a future release of netCDF 4.1 (whic is 
now in
the past).  Thanks for pointing out these documentation problems.

It may be helpful to look at this Appendix, which also addresses HDF5 features 
and
how netCDF-4 uses them and which applies to the 4.1.1 release:

  http://www.unidata.ucar.edu/netcdf/docs/netcdf.html#NetCDF_002d4-Format

See especially the subsections on shared dimensions and dimension scales.

--Russ


Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: EEP-446216
Department: Support netCDF
Priority: Normal
Status: Closed