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Re: [ddlm-group] Draft EBNF for CIF2

  • To: ddlm-group <ddlm-group@iucr.org>
  • Subject: Re: [ddlm-group] Draft EBNF for CIF2
  • From: James Hester <jamesrhester@gmail.com>
  • Date: Fri, 22 Aug 2014 10:26:42 +1000
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Dear DDLm group,

John Bollinger has reminded by of a further change: nested save frames, which were introduced in the STAR2 and DDLm papers, are included in the EBNF.  CIF1.1 only envisioned a single level of save frames, and only in dictionary files.  Absent a decision by this group or COMCIFS, the restriction of save frames to dictionary files (nested or otherwise) would continue.

James.



On Wed, Aug 20, 2014 at 4:33 PM, James Hester <jamesrhester@gmail.com> wrote:
Dear DDLm group,

John Bollinger and myself have put our heads together and produced an ISO 14977 EBNF specification of CIF2.0 syntax.  We were working from the 10 August 2011 "CIF Changes" document agreed by this group and approved in Madrid, available in the archives of this list at http://www.iucr.org/__data/iucr/lists/ddlm-group/pdf00001.pdf, with the following change:

(1) triple-quoted strings were returned to the specification as agreed in Montreal, in the form contained in the draft posted at http://www.iucr.org/__data/assets/pdf_file/0020/59420/cif2_syntax_changes-jcb20110728.pdf

Please study the attached EBNF (plain text format) and advise of any errors, omissions or ambiguities.  Note that EBNF is clearly not the best format for machine-generation of parsers, but it should be sufficiently precise and understandable to serve as a foundation document for CIF2.

For those, such as myself, who have not seen the ENBF '-' operator before, the meaning of "A-B" is: all character sequences satisfying A, except those that satisfy B.

My intention is to start producing documentation for CIF2 on the basis of this EBNF, so your earliest comments would be most appreciated.

all the best,
James.

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