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RE: The CIF BNF

  • Subject: RE: The CIF BNF
  • From: "Bollinger, John Clayton" <jobollin@xxxxxxxxxxx>
  • Date: Thu, 21 Sep 2000 14:59:35 +0100 (BST)

Herbert Bernstein wrote:
> However, I also believe it is time to extend the concept of a "CIF" to
> include files with other line length limits (to be specified in the
> relevant dictionary), so that I would suggest the BNF specify the
> existence of a limit, giving 80 characters as an example, rather than
> as an intrinsic part of the definition of a CIF.  

Well, right now the 80-character limit _is_ an intrinsic part of the
definition of a CIF.  If one just modifies the BNF then the result
no longer describes a CIF -- one must first persuade COMCIFS to alter
course on the CIF specification.  My impression is that COMCIFS has
historically resisted suggestions to modify the limit.

As for the 80-character limit itself, I should like to see it lifted
entirely.  I very well appreciate that that would cause problems for
Fortran programmers trying to deal with CIFs, but that argument is like
the tail trying to wag the dog.  I also recognize that the 80-character
limit can make CIFs more readable in certain display and printing
environments, but few people are limited to such environments.  On the
other hand, the limit is completely artificial, in that it is in no way
driven by the content of the file; and it introduces unnecessary
software compatibility issues, in that the handling of violations of
the limit is not defined.  Removing the limit would make it easier to
adapt STAR parsers for CIF and vice versa.  Why retain it in any form?

Regards,

John Bollinger

--

John C. Bollinger, PhD
Indiana University
Molecular Structure Center

jobollin@indiana.edu

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