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Re: Response to Pflugrath

  • To: Multiple recipients of list <imgcif-l@bnl.gov>
  • Subject: Re: Response to Pflugrath
  • From: "J.W. Pflugrath" <JWP@msc.com>
  • Date: Fri, 12 Jan 1996 10:11:06 -0500 (EST)
David Brown comments:

>>...
>> Everyone agrees that the headers could be given in ASCII and could be
>> therefore be structured as cifs.  At some point the images are going to be
>>...

>> 	2. Cifs are composed of character strings and line feeds.  There 
>> is no provision for blocking the contents into multiples of 512 
>>...

>> 	3. A key feature of cif is that each keyword is followed by a
>> single value.  Multiple values as proposed by Jim are not allowed. 
>> However, they can be given using a loop structure, so this is not
>> necessarily a serious limitation. 
>>...

>> 	The question that needs to be decided at this stage is whether it
>> is possible to implement the image file within cif.  If it is not, then we
>> should address the problem of creating an image file structure that allows
>> easy interchange with cif for all fields except the image.  Before any file
>> structure can be established for images, it is essential to clarify to
>> what extent such a file will be cif-compliant or cif-compatible.  By
>> cif-compatible I mean that the concepts contained in each file will be the 
>> same so that transcription between the two file types is trivial. 

and I respond:

I have no heavy investment in blocked images (512 or otherwise), though Rigaku 
R-AXIS images are blocked.  So I will not rigorously support my blocking 
suggestion for the header.

Also I am not adverse to dropping the formfeed suggestion, as long as I can 
put a formfeed in a comment field.  It would not be a requirement though.  
However, there is little substantive difference between a linefeed and a 
formfeed: both are ASCII characters.

A single value for each keyword is OK with me.  If you allow multiple
values, then you do not need as many keywords and I feel bookkeepping is
simpler. It is certainly no hardship to have a single value.

Thus, I think it is possible to have a cif-compliant/compatible header 
for images and I am all for it.

So David, what would the CIF syntax be for the file header suggested
in my first posting?

Jim

PS: Where can I obtain the "definitive" definition of CIF and existing
keywords?

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