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Re: CIF 2.0 syntax proposal for retaining backwards CIF 1.xcompatibility

  • To: "Discussion list of the IUCr Committee for the Maintenance of the CIF Standard (COMCIFS)" <comcifs@iucr.org>
  • Subject: Re: CIF 2.0 syntax proposal for retaining backwards CIF 1.xcompatibility
  • From: yayahjb <yayahjb@gmail.com>
  • Date: Mon, 16 Sep 2013 07:37:13 -0400
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My suggestion is that we consider the CIF2 syntax a closed issue, but instead usethis as an opportunity to consider how best to deal with the mapping between CIF2files and CIF1 files when needed, inasmuch as both languages will be with us atthe same time.  -- Herbert


On 9/15/13 10:58 PM, James Hester wrote:> Reply to Saulius's suggestions of altered syntax.> ===================================>> It was decided early on that the CIF2 standard would not be backwards> compatible with the original standard. Rather, we would allow> ourselves to be disruptive in order to add the new datastructures for> DDLm and to fix deficiencies in CIF1. We therefore called the new> standard CIF2, rather than (for example) CIF1.2.  In addition, we> undertook to allow CIF1 to exist for as long as necessary, with no> coercion to move to CIF2. For background, see the messages in the DDLm> list dating from September/October 2009.>> So incompatibility with CIF1 is not, in itself, news and is not> sufficient to justify changes to a syntax that has been sweated over> for many years.>> In particular, the drawbacks identified by Saulius are:>> (1) Users will need to learn different rules.>> Yes, we have accepted this as part of the change>> (2) Developers will need to produce two distinct grammars and parsers>> Yes, we have accepted that this will be the case.>> (3) Auto-choosing between CIF1 files and CIF2 files is problematic for > non-seekable> files if the header is lost>> The CIF2.0 header is a required part of CIF2. I do not believe that> the first line of a file is lost that often, if ever.>> Regarding the syntax suggestion itself: while it is likely to be the> most elegant way to maintain CIF1 compatibility (if we felt that> worthwhile) while still making it possible to present something> that looks vaguely like a table, it still falls short of a compelling > idea, because it gives> '[ [' and '[[' different meanings, which is counter-intuitive and a step> backward towards the CIF1 approach of giving whitespace extra > significance.>> It is to avoid such contortions that we agreed to allow> incompatibility between CIF1 and CIF2.>> We need to avoid any further major syntax changes in CIF2. Closing> the book on syntax changes results in a precise understanding of> the differences between CIF1 and CIF2, so we can meaningfully explore> managing CIF1-CIF2 transitions in alternative ways, e.g. through> documentation and policy.>> On Thu, Aug 29, 2013 at 8:54 PM, Saulius Gražulis <grazulis@ibt.lt > <mailto:grazulis@ibt.lt>> wrote:>>     Dear COMCIFS members,>>     as we have discussed during the recent IUCr Data Management>     workshop, I>     have put together a proposal for the CIF 2.0 syntax that is fully>     backwards compatible with CIF 1.1. I attach a draft of this proposal>     (see the attached "CIF1-CIF2-compatibility.txt" file). The new>     proposal>     uses '[[' and ']] to delimit tables (instead of '{' and '}'), and>     retains the syntax of CIF 1.x quoted strings.>>     James has offered to try to "break" the proposed syntax, i.e. to>     see if>     it can be parsed correctly in all kinds of unusual cases. I have done>     preliminary tests of this kind using my sample implementation; the>     tests>     I have used are attached as the "breakit.zip" file (it features 6>     correct cases and 5 incorrect syntax examples). My impression is that>     the proposed '[['/']]' syntax can always be parsed as expected, and>     syntax errors an be unambiguously detected.>>     I would be grateful for comments from the COMCIFS members and, if the>     proposal is found to be acceptable, for consideration of its inclusion>     into the forthcoming CIF 2.0 standard.>>     Sicnerely yours,>     Saulius>>     -->     Dr. Saulius Gražulis>     Vilnius University Institute of Biotechnology, Graiciuno 8>     LT-02241 Vilnius, Lietuva (Lithuania)>     fax: (+370-5)-2602116 <tel:%28%2B370-5%29-2602116> / phone>     (office): (+370-5)-2602556 <tel:%28%2B370-5%29-2602556>>     mobile: (+370-684)-49802 <tel:%28%2B370-684%29-49802>,>     (+370-614)-36366 <tel:%28%2B370-614%29-36366>>>     _______________________________________________>     comcifs mailing list>     comcifs@iucr.org <mailto:comcifs@iucr.org>>     http://mailman.iucr.org/mailman/listinfo/comcifs>>>>> -- > T +61 (02) 9717 9907 <tel:%2B61%20%2802%29%209717%209907>> F +61 (02) 9717 3145 <tel:%2B61%20%2802%29%209717%203145>> M +61 (04) 0249 4148 <tel:%2B61%20%2804%29%200249%204148>>>> _______________________________________________> comcifs mailing list> comcifs@iucr.org> http://mailman.iucr.org/mailman/listinfo/comcifs>    
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