Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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: Thu, 18 May 2000 14:08:10 +0100 (BST)
On May 17,  8:19pm, Bollinger, John Clayton wrote:
> You are missing two things; or actually, two sides of the same thing.
> 1) Part of the purpose of BNF is to provide an authoritative
>    description of exactly which constructs are valid "utterances"
>    of the language described.  It is not just a description of how to
>    write a parser for that language that provides the expected
>    answers in a particular software context.

> It will be clear now that I have come around in my thinking about
> whether a full BNF description of CIF would be desirable.  I definitely
> think it would be.

After reading your comments John and examining the various pathalogical cases
I am coming to the conclusion that ANY reading of a CIF should be done by a
full-blown parser based on a complete BNF descriptor of the "CIF language"
(with whatever changes to the CIF syntax necessary to allow such a descriptor
to be made). Even examining a file to see if there are multiple datablocks
seems to need a complete parsing to ensure the correct extraction of the
block identifiers. Fortunately, given the memory and speed of today's
machines, I don't think this is such an onerous requirement; the CIF can be
parsed in a single pass over the file and all dataitems held in memory to be
supplied to the calling program as and when needed.

Given the above, a fast efficicient parser easily interfaced to a number of
languages and supported by the IUCr does seem the best approach. Such a
parser could be the basis for a CIF-prettifier, a CIF-lint (vcif Mark II ?),
a CIF-editor (edcif ?), CIF-database (dbcif ?), ... :-)


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

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Science Council (admitted 1947). Member of CODATA, the ISC Committee on Data. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

International Science Council Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.