[Nexus] Correct way to specify multiple signals

[V. Armando Solé]

Hi Jacob,

Sure, I can send you my proposal as I have it ready since long ago as
part of my recommendations for the ESRF. The text is extracted from
https://gitlab.esrf.fr/sole/data_policy/blob/master/ESRF_NeXusImplementation.rst

Probably you will see it better by clicking the previous link and going
to the relevant section, but the relevant part follows:

**Processed Data**
Our goal is to store a maximum of information and to minimize the number
of files. All that can be achieved creating an HDF5 group with
information related to each data processing step in which it is critical
to have

Program used
Configuration paramters
Results
Order in the data treatment sequence

In the NeXus convention this can be achieved by using a slightly
extended NXprocess group:
entry/
entry/start_time
entry/end_time
entry/title
entry/process_name at NXprocess
entry/process_name/program
entry/process_name/version
entry/process_name/date
entry/process_name/sequence_index
entry/process_name/configuration at NXcollection if the analysis code
understands HDF5
entry/process_name/configuration at format=“ini” or whatever … if string
entry/process_name/results at NXcollection or NXdata if plot

The extension to the original NeXus NXprocess description is the
configuration and results fields. Probably this can be brought closer to
NeXus conventions by adding some of the concepts of the NXnote class
like file_name and type (containing Mime content type) as attributes of
the configuration entry. This is particularly interesting in the case
the configuration consists on a binary representation of a file
understood by the analysis program.