[Nexus] unit_cell in NXsample

[Pete R. Jemian]

It would be more sensible to describe each term separately rather than 
rely on this arcane coding of the terms.  If this definition is to be 
revised, I suggest creating fields for each of these terms:
a
b
c
alpha
beta
gamma

Otherwise, we need to relax the units attribute.  A value of "NX_LENGTH 
or NX_NX_ANGLE" (or syntax that can be properly coded in XML) looks 
sensible to the eye but I'm not sure if we have the XML Schema support 
for this.  Yet.  For now, NX_ANY is the only existing value that spans 
what is proper.  An alternative is to introduce a new unit type 
NX_LATTICE_PARAMETER which could be either length or angle.

No good answer for now.

Pete

On 09/17/2014 11:48 AM, Tobias.Richter at diamond.ac.uk wrote:
> The unit_cell in NXsample is defined like this:
>
> <field name="unit_cell" type="NX_FLOAT" units="NX_LENGTH">
>
> <doc>Unit cell parameters (lengths and angles)</doc>
>
> <dimensions rank="2">
>
> <dim index="1" value="n_comp"/>
>
> <dim index="2" value="6"/>
>
> </dimensions>
>
> </field>
>
> Since it already says “lengths and angles” the fact that the required
> units are NX_LENGTH is a bit puzzling. No units for the angles?
>
> Would it be sensible to have “length_units” and “angle_units” attributes?
>
> Tobias
>
>
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