[Nexus] question about NeXus classes

[Darren Dale]

I guess I should also report that all of the nexus test files I have attempted 
to validate from the svn checkouts have failed on NXdata groups. Is there a 
problem with the definition of NXdata at 
http://definition.nexusformat.org/schema/3.0/NXdata.xsd ? It does not seem 
compatible with the discussion of NXdata at http://www.nexusformat.org/Design.

Thanks,
Darren

On Thursday 18 December 2008 10:50:13 Darren Dale wrote:
> Hello,
>
> > > On Friday 25 July 2008 13:35:13 Peterson, Peter F. wrote:
> > > > The current philosophy of classes is that they are to be thought of
> > > > as dictionaries. If you are familiar with xml schema (xsd) the "any"
> > > > tag is appropriate. This means that there is one NXdetector which
> > > > covers all the various types of detectors in existence. If a
> > > > particular detector needs another field that isn't in the current
> > > > NXdetector, then it should be added. Subclassing is not an idea that
> > > > can be applied to the base classes.
>
> I am revisiting NeXus compatibility, and am experimenting with adding some
> additional metadata (like the dimensions of a scan or some additional
> information to choose a more specific object constructor in python)...
>
> On Wednesday 27 August 2008 10:29:12 Mark Koennecke <Mark.Koennecke at psi.ch>
>
> wrote:
> > > On Saturday 26 July 2008 09:42:04 am Darren Dale wrote:
> > > Today I discovered nxvalidate in the nexus trunk and tried running it
> > > on some of the test files in test/data. They either did not conform to
> > > the new 3.0 schema or the perhaps the schema does not include all the
> > > definitions needed to validate these files.
> > > nexus_defs/schema/testfile.xml does validate. Is there any additional
> > > information available concerning the new organization of NeXus
> > > classes/subclasses, new features, etc?
> >
> > The files in test/data are there to test some mechaniques of the API.
> > They do not conform to the standard. I apologize for this, but NeXus is
> > maintained by very
> > people in their spare time and thus we are not always as consistent as
> > would be
> > desirable. But worry though( and try to resolve the issue) if your files
> > fail the nxvalidate
> > test.
>
> If I include attributes in my file that are not in the NeXus definition,
> like at the root level if I have an HDF5_API_version attribute, nxvalidate
> complains that the attribute is not allowed. So I am confused, I thought I
> understood from Peter's response that I can use additional attributes and
> fields and remain valid so long as I use the existing NX_classes.
>
> Also, I would like to include a group under NXentry that contains the most
> relevant information from the measurement, like datasets for the scanned
> counters and motors, to make it easy to find interactively work with this
> data like you would in Matlab or IPython. Is it valid to create generic
> HDF5 groups that do not identify a NX_class attribute?
>
> Finally, nxvalidate complains about finding an NXinstrument definition in
> NXentry, is that an error in the NXentry schema definition? The description
> at http://www.nexusformat.org/NXentry shows NXinstrument, but it does not
> appear in http://definition.nexusformat.org/schema/3.0/NXentry.xsd .
>
> Thanks,
> Darren
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