[Nexus-developers] Scattering application definition

[Mark Koennecke]

Hi,

Pete Jemian already pointed out a couple of problems with the NXDL.
I have a few points to make about the content:
- In general the application definition is very close to what NeXus does.
- The scattering application definition defines coordinate systems for 
incoming beam,
   sample and detector. Here are some issues:

   * NeXus is  trying to come up with a system which emulates the CIF 
way of doing coordinate
     systems. I admit that we are very slow on this, possibly because it 
takes a crystallographer
     to understand and sort such things out. Rainers system would be in 
conflict with this.
   * The scattering application definition stores positions as separate 
x,y,z and rotation matrices
      as individual components, xx, xy, ...... Now, I would prefer to 
store this as array position[4] and
      orientation[3,3]. Or may be, the whole lot together as a 4x4 matrix.

- Time stamps. NX_DATE_TIME is in ISO8601 which alllows to have the 
seconds with as much precision as
   required. Time offset can be floating point values. Thus the NeXus 
time recording system is accurate
   enough.
  - In the detector group the name data is first used for what I call 
dimensions (data[1],data[2]) and later
    for the actual detector data. I assume that this is a typo and that 
in the first case dim[] was really meant.
    Otherwise I do not understand this. Strictly speaking, a separate 
field for dimensions is not necessary
    as the attributes to the detector data already contain that 
information (rank and dims).
- Otherwise there are just a few new names which have to synchronized.

Sorry that this response took to long.....

Best Regards and Happy Easter,

                Mark Koennecke