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Convergence ?


I direct this e-mail mainly at COMCIF (through David and Brian), but
clearly it's relevant to everyone. I feel that some convergence has
been taking place, and I'd like to confirm this view from the COMCIF 
members.

1. Do we have concensus on the binary nature of storage for the "image"
   data ? (As opposed to ASCII encoding of "image" data.)
 
   My view is yes, and essentially an unanimous view. Everyone involved
   closely in "imaging" who has a given an opinion is clearly in favour of
   binary. (This coincides with existing practice !)

2. Do we have concensus on holding header information and binary "image"
   information together in the same file ? ( The main alternative to
   this would be to have a separate header file which could therefore be
   a pure text file, and a binary file for the "image" data.)

   My view is yes. This slightly less clear, but there is nevertheless
   a clear majority favouring this.

If 1. and 2. are accepted then we are talking about something
different to CIF, but hopefully simply related to CIF ("cif-compatible"
but not "cif-compliant").

3. Within the COMCIF framework could a "Crystallographic Binary File"
   (or similarly named) format be defined ? With a "CIF-compatible" 
   header section, and a tool to convert the "cif-compatible" header 
   sections to "cif-compliant" files.

If 3. is accepted then we could start defining the major details of how
this would work, and maybe it would be timely to "advertise" more widely
the initiative.

4. Should some information be made generally available ? e.g. 
   IUCr WWW CIF page, IUCr newsletter, Talk/Discussion at Seattle in 
   August, etc.

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(

David's example of a possible CIF style header shows nicely how such
a header might look. I have one comment on this which I feel is
sufficiently general and important to mention at this stage:

   We should avoid the term "image" except when we are clearly talking
   about images. (I called the initiative "imageNCIF", but maybe
   "binNCIF" would have been better, but then again maybe not). I think 
   potentially the file could contain binary data which is not of
   "image" nature or even simple multi-dimension array. I would propose 
   "_binary" replaces "_image". A keyword value pair such as:

   _binary_data_class image # Binary data is a simple 2-D array

   could be defined along with permitted values to allow programs to
   easily identify the type of data which is stored, and therefore the
   necessary keywords.

   Of course I still believe initially we should concentrate on "images".

)
------------------------------------------------------------------------------

                 Andy Hammersley

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