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Re: Backus-Naur descriptions for STAR and CIF

  • Subject: Re: Backus-Naur descriptions for STAR and CIF
  • From: Brian McMahon <bm@xxxxxxxx>
  • Date: Wed, 17 May 2000 16:56:04 +0100 (BST)
Nick, John

Couple of quick thoughts as I leave... I'll review the CIF BNF in detail on
the plane.
 
> > Hence for CIF data files - as originally envisaged - the save_ and global_
> > restrictions should apply; and Nick's BNF is erroneous.
> 
> I am happy to update the CIF BNF accordingly, if you give me the go ahead
> Brian. If I read you correctly the DDL1 based dictionaries will follow the
> same BNF except that one can explicitly enumerate the allowed datanames.

OK Nick, please delete the <global_block> and its dependent entries. I
am not sure about enumerating the allowed datanames in dictionary files -
I'd say not, unless it helps in building validators mechanically.

> > What about designating the end of looped data with "stop_"?
> 
> It is provided for within the BNF but not mandatory. Therefore its
> presence or otherwise still makes for a consistent CIF.

Hmm - vcif certainly chokes on "stop_" in a CIF. Nick, can you discuss this
with Syd Hall? I suspect that many existing CIF applications, written by
crystallographers who have only read the Acta paper, would break if they hit
a stop_.
 
>                                                                    English
> prose is expressive but unfortunately easily open to misinterpretation. 

As amply demonstrated here :-)

These discussions are very useful in identifying misinterpretations and
points for clarification that will find their way into the FAQ and the web
documentation tree when I get the chance.

Best wishes
Brian

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