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Re: CIF parser / dialects

  • Subject: Re: CIF parser / dialects
  • From: Brian McMahon <bm@xxxxxxxx>
  • Date: Wed, 10 Jul 2002 13:49:01 +0100 (BST)
I agree with James' approach: since you cannot sensibly oblige people to use
a specific piece of software, people will in any case write their own
parsers. (That is not to deny that robust and reliable off-the-shelf parsers
would be helpful for folks who don't want to roll their own.)

Indeed, what is required is an extensive set of trip tests that could be
used as the basis for self-certification of a parser. It turns out that
no two existing CIF parsers agree completely on the handling of some of the
more subtle syntax features. For some time a working group within COMCIFS
has been trying to nail down the ambiguities and subtleties, and I shall in
a separate message introduce to the list the current draft of the
specification for community review.

I am sure that the final version of this specification, when adopted and
ratified by COMCIFS, will require new trip files to test parsers for full
compliance, and I shall welcome help in assembling such a suite in due

Best wishes
Brian McMahon                                             tel: +44 1244 342878
Research and Development Officer                          fax: +44 1244 314888
International Union of Crystallography                  e-mail:  bm@iucr.org
5 Abbey Square, Chester CH1 2HU, England                         bm@iucr.ac.uk

> On Wed, 2002-07-03 at 03:00, Richard G. Ball wrote:
>> If there is a concern over CIF dialects the easiest way to allay that
>> concern and inhibit present and future dialects is to provide an IUCr
>> sponsored parser. It should be in C and easily interfaced with the
>> usual development languages ...
>>              The situation we have now, with so many disparate parsers,
>> is not very satisfactory ... and really should be addressed.

On Wed, Jul 03, 2002 at 05:06:42AM +0100, James Hester wrote:
> I think this proliferation is both inevitable and to be encouraged. 
> Inevitable, because every author has different needs and circumstances
> governing their choice of language:
> To be encouraged, because sooner or later there will be a parser for
> everyone in the language they choose, thus lowering the barrier to the
> spread of CIF software, and because, once some sort of official blessing
> is obtained from the IUCr, there will be multiple reference
> implementations.
> Which brings me to my final point (made a long time ago already on this
> list or COMCIFS): given that inevitably others will want to write native
> Perl/Lisp/Assembler parsers, a set of tricky tests which can be used for
> automatic verification of a parser would be a key step forward.

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