[NeXus-committee] NXroot is required - or should be made so

[Herbert J. Bernstein]

Dear Colleagues,

  This is actually a trickier and more subtle issue than it might at
first appear. And HDF5 "file" is actually more like a file system in
which it is perfectly legitimate to nest multiple HDF5 trees into a
larger one.    More than one completely independent NeXus file could
easily exist within the same overall HDF5 file serving as the file
system.  What I would suggest is:

"The root of a NeXus file has the attribute NX_class="NXroot" as a
node within an HDF5 file.  Most commonly, but not necessariiy, that
node will also be the root of the containing HDF5 file.  If a NeXus
file is started with an NXroot further down in the containing HDF5
file, the nodes of the NeXus file will not refer to nodes outside
NeXus file, except through the HDF5 external link mechanism, just as
if they were is different files."

  Regards,
    Herbert

On Thu, Aug 28, 2014 at 11:57 PM, Osborn, Raymond <rosborn at anl.gov> wrote:
> Is this a ratified decision? I’m still not sure why this is necessary.
>
> Ray
>
> On Aug 28, 2014, at 11:23 AM, Pete Jemian <prjemian at gmail.com> wrote:
>
>
> require that the attribute NX_class="NXroot" is assigned to the root of the
> HDF5 file
>
> On 8/28/2014 11:20 AM, Osborn, Raymond wrote:
>
> I’m not sure I’m understanding this correspondence. NXroot is the root level
> of the HDF5 file. When you read in the file, it might have some meaning as
> the root of the file tree, but within the HDF5 file, it doesn’t exist as a
> separate entity, so what does it mean to ‘require’ it?
>
> Ray
>
>
> On Aug 28, 2014, at 10:51 AM, Pete Jemian <prjemian at gmail.com> wrote:
>
> yes
>
> On 8/28/2014 10:50 AM, Joachim Wuttke wrote:
>
> Shouldn't the manuscript describe best practice as of now,
> regardless of compatibility issues?
>
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> --
> Ray Osborn, Senior Scientist
> Materials Science Division
> Argonne National Laboratory
> Argonne, IL 60439, USA
> Phone: +1 (630) 252-9011
> Email: ROsborn at anl.gov
>
>
>
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