[NeXus-committee] questions about NeXus data structures as per Figs 1-3 of draft paper

[Joachim Wuttke]

Dear colleagues:

In the draft manuscript (v6), Figs 1 and 3 show the
common structure of raw-data and processed-data
files, respectively.

Are these structures also described in the docs? Where?

Some groups are marked as "required". Is this specified
in the docs? Where?

If some groups at second or third level are required,
then the first-level group "NXroot" must also be
required, right?

Why should we require NXdata? If scientists at a certain
instrument have no interest in using generic default
plotting tools, and don't like the extra complexity of
symbolic links in their raw data files, we should allow
them to use NeXus without NXdata.

Why is NXinstrument required for raw-data files? Is there
an application definition without an NXinstrument group?

It seems though that there are some raw-data application
definitions without NXsample, and many without NXuser.
Is there a rationale why some instrumt types would
require these metadata, and others not? Or do the
different application definitions just reflect different
personal preferences of different authors?

For multi-method instruments, some entries move from
NXentry into NXentry/NXsubentry. What if one day an
established multi-method instrument gets embedded into
a yet more powerful instrument: will we then have
NXentry/NXentry/NXsubentry or NXentry/NXsubentry/NXsubsentry
or NXentry/NXsubentry/NXsubsubsentry? In my humble
opinion, NXsubentry should never have been invented;
why not use the power of recursion and allow NXentry/NXentry?

Best - Joachim

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