High there,

  a colleague of mine is working on a fitting program and wants to read
  NeXus data. He found something with the data vGroup which might be a real
  issue: How to automatically decide what is the main data content? This is not
  completely clear to me. I can think of two options to resolve this:
  - We prescribe, that the data vGroup may contain only data + axis attributes
    with NO auxiliaries. 
  - We put an attribute signal=1 on to the main data content. This is reviving
    an idea from John Tischler.

  I'll opt for the second option because it leaves us the freedom to have
  auxilliary data, for instance temperature or certain angles, in the
  data vGroup. Such data can make sense there because sometimes such data
  is necessary even for a first glance. For example: On a four circle
  diffractometer equipped with an area-PSD a detector frame without information
  about setting angles is utterly useless. Except if all you want  is to look 
  at boring pictures with spots.

  What does everybody else thinks?

                                            Mark Koennecke