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Re: Backus-Naur descriptions for STAR and CIF

  • Subject: Re: Backus-Naur descriptions for STAR and CIF
  • From: "Richard G. Ball" <richard_ball@xxxxxxxxx>
  • Date: Wed, 17 May 2000 17:55:03 +0100 (BST)
On May 17,  5:10pm, Bollinger, John Clayton wrote:
[snip]
> Here is a very important question, however: are all the pertinent
> restrictions expressible in BNF?  I have been reading up on (E)BNF, and
> I haven't figured out a reasonable way to express the 80 characters/line
> restriction that CIF specifies.  The only techniques I can imagine are
> absurdly complex, and I'm not even sure they would work.  If we can't
> write a useful BNF-only description for CIF (or another STAR dialect)
> then the question is moot, and we must instead ask how many of the
> restrictions of a particular dialect, if any, do we want to express in
> BNF form, and how will we express the remaining ones.

Isn't the 80 chars/line something that is only relevant for CIF writing
 (including dictionary creating) programs? The BNF spec. for the parser
doesn't need to worry about it since the parsing of the incoming file can be
record length independent. Once the stream has been tokenized then such
additional restrictions as length of datanames or datavalues can be applied
and error condtions raised. Or am I missing something?

Richard

--
Dr R.G. Ball                    |  voice: 732-594-5341
Merck Research Laboratories     |  fax: 732-594-6793 or 6100
PO Box 2000, R50-105            |  email: Richard_Ball@merck.com
Rahway, NJ  07065   USA


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