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Re: Backus-Naur Form for CIF

Dear Syd,

	As you point out there has been a private discussion going on
proposing to relax the 80 character line restriction in CIF and I hope to
move this discussion to this list as soon as there is a concrete proposal
to be brought forward.  This is an important change to CIF and all members
of this list need to know exactly what is proposed and to have an
opportunity to comment on it.  The proposal, when it is presented, will
probably suggest that we introduce a new version number for CIFs that
allow more than 80 characters to a line, so that we have a way of
identifying whether a CIF is compatible with software written in
compliance with an earlier version number.

	Clearly as things stand at the moment, the 80 character line limit
is in place so the BNF for CIF is currently correct.  Adding Herbert's
caveat does not change the BNF, it only warns users of likely changes so
that they can be prepared.  When Comcifs approves a relaxation of the line
limit we can either change the BNF or prepare a second BNF for the new
version depending on how Comcifs eventually decides to handle the change.  
For the time being we are only approving a BNF that described CIF as it
now exists.


Dr.I.David Brown,  Professor Emeritus
Brockhouse Institute for Materials Research, 
McMaster University, Hamilton, Ontario, Canada
Tel: 1-(905)-525-9140 ext 24710
Fax: 1-(905)-521-2773