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Comments of prototype CBF

> 
> 	Andy is to be congratulated on his prototype CBF description 
> which seems to me to be admirable and incorporates most of the consensus 
> that has developed.  My comments are relatively minor.
> 
> 	I am inclined to agree that 'image' should be replaced by 
> 'array'.  An image is stored as an array, but not all arrays will contain 
> images.  An array is a matrix of numbers which may or may not have a 
> spatial distribution, so let us not confine ourselves to those that only 
> describe images.
> 
> 	Why then stop at the 2-D definition?  The third dimension is a 
> trivial extension of 2-D, so it costs little to include it in the present 
> definition and it almost certainly will be needed at some time.  How many 
> more dimensions will be needed is not clear.  Maybe none, but others can 
> be added as required by future extensions.  In any case there is an upper 
> limit on _image_size_dimensionality of 2 or 3.  No more dimensions can be 
> used than the CBF definition allows.  I notice that you have not defined 
> _image_size_dimension_* (*=1,2,3) and a couple of other data items used 
> in the example, but I assume they will be added in the next version and 
> their meaning is pretty clear for the present.
> 
> 	Some of the fields that you define are indeed more suitable for 
> images than arrays, but that should not be a problem.  They only need to 
> be used if the array contains images. 
> 
> 	You imply that several images can be given in sequence, but they 
> must all have the same characteristics.  This should not be necessary if 
> you allow the descriptors in the header to be looped.  Thus the header 
> could describe a number of different images that follow in sequence.  
> However, it is not legal in cif to mix items from different categories in 
> the same loop, so it might be difficult to describe what information the 
> array contained, even though its layout would be well described.
> 
> 	Is it clear how one array is terminated and a second begun when 
> the cif contains multiple arrays?  What is the normal method of 
> terminating a binary array?  Are there separators in the binary string 
> that can be used for this purpose?
> 
> 	Will all area detectors be oriented perpendicular to the main 
> beam?  Is it necessary to consider the possibility of theta having a 
> value other than zero?  Are the terms horizontal and vertical too 
> restrictive?  What if the array has no obvious spatial orientation or if 
> someone insists on having a main beam that is vertical?
> 
> 	The definitions are very clear and unambiguous.  A delight to use.
> 
> 			Congratulations!
> 
> 				David Brown
> 
> *****************************************************
> Dr.I.D.Brown
> Brockhouse Institute for Materials Research, 
> McMaster University, Hamilton, Ontario, Canada
> 1-(905)-525-9140 ext 24710
> *****************************************************
> 
> 
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