[NeXus-committee] NXgroup: undocumented or inofficial?

[Pete Jemian]

Joachim :

The text "NXgroup" does not appear in the manual, nor in any NXDL 
definition.

NXgroup is not defined by NeXus.  This is actually a NeXus rule, 
although it might be expressed more clearly in the documentation, it 
seems.  Here are the two relevant references I found for "prefix":

* http://download.nexusformat.org/doc/html/design.html?highlight=prefix

   "For the class names used with NeXus data groups
    the prefix NX is reserved."

* 
http://download.nexusformat.org/doc/html/applying-nexus.html?highlight=prefix

   ... "and do not use the prefix NX for your classes."

Additional content about this rule provides the definitive answer:

* http://download.nexusformat.org/doc/html/introduction.html?highlight=begin

   "The class types, which all begin with NX, define
    the sort of fields that the group should contain,
    in this case, counts from a beamline monitor."

The strongest definition of this rule appears here:

* http://download.nexusformat.org/doc/html/design.html?highlight=begin

   "All NeXus class types adopted by the NIAC must begin with
    NX. Classes not adopted by the NIAC must not start with NX."


The SNS should be advised to change this use of NXgroup to one of the 
existing NeXus base classes.  The SNS data files with NXgroup groups 
should not be considered as examples of fully-compliant NeXus data files.

Pete



On 7/8/2014 10:33 AM, Joachim Wuttke wrote:
>  From a SNS sample file, I learn that there is
> a NeXus class "NXgroup". However, I do not find
> it in the PDF doc, release 3.1.
> Is this a bug in the doc, or is NXgroup an
> unofficial extension?
> - Joachim
>
>
>
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