No subject

 -  Global IDs should not be interpolated because they are labels, not 
"numbers"
 -  Global IDs should not be copied either, unless doing so preserves 
meaning.
 -  Passing through is usually OK because it is 1:1.
 -  Must be of type vtkIdType.
 -  Must be unique?

and PEDIGREEIDS

- Pedigree IDs should not be interpolated because they are labels, not 
"numbers"
- Pedigree IDs may be copied since they do not require 1:1 mapping.
- Can be any type.
- Need not be unique?


For example, if all my points are given unique labels of type vtkIdType, 
some having the same coordinates (coincident), these would seem to fall into 
the GLOBALIDS category. Given a line cell with point labels 8 & 9 (say), it 
doesn't make sense to interpolate these labels if it is cut or clipped but 
given vertices with point labels 10 & 11 (say) clipping would preserve 
meaning.

Any help would be much appreciated.

Thanks,

John.