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Re: [ddlm-group] The Grazulis eliding proposal: how to incorporateinto CIF?. .. .. .

Dear Colleagues,
I have looked more carefully into the CIF2.0 syntax proposal, and wouldlike to present some thoughts as a manager of a crystallographic datarepository (COD in my case).
Most changes are indeed very welcome and useful. I am especiallyenthusiastic about adoption of UTF8!
I am happy to see my prefixing proposal being considered for inclusion.
There is one change, however, that would cause major problems for me asa CIF user: this is the proposal to change the single- and double-quotedstring handling in a way that is incompatible with CIF 1.x
No matter how "good" or "bad" any of the string handling conventionsare, we need to face the fact that CIF 1.x is already used, widespreadand there exists a large number of archival CIF 1.x records that need tobe maintained. Changing interpretation of a closing quote, andforbidding quotes in the similarly-quoted strings would cause majorproblems for archives:
a) the old CIF1.x records will need different parser, or a differentparser mode. This mode can not always be determined automatically fromthe file contents (the #\#CIF... magic sequence is a comment, it can bediscarded and thus we can not rely on it. Besides, it can be plainly wrong).
b) Both archivers and users will need to care about which kind of CIFthey have. Ideally, every existing CIF1.1 CIF should become a validCIF2.x CIF.
c) Most people will find it extremely confusing if CIF1 rules forstrings are substantially different from CIF2. I have put some effort inteaching people how to quote CIF strings; imagine they will now have tolearn *both* CIF1 and CIF2 rules, that are arbitrarily incompatible.
d) The current Change 6 ("delimited string"), IMHO, does not solve enyproblems. The CIF string handling was made different from the stringhandling in the C programming language -- an unusual but definitely aworking construct. And it is definitely quite good -- it just works ).Yes, one needs to put some effort to learn it -- but the same holds forthe C-style strings, or for the new CIF2 proposal.
Given the enormous work of useless work that the new quoted stringsyntax would put on CIF authors and maintainers, I would be extremelyhappy to see the CIF2 development implemented along the lines suggestedby Herbert, as quoted below:
Herbert J. Bernstein wrote:
> I suggest we complete the process and restore the CIF1 parse for all> quoted strings, i.e., that we _not_ terminate a quoted string scan for> the terminal quote on the first occurrence of the terminal quote,> but only on the first occurrence of the terminal quote followed by> white space.>> The only place in DDLm where this causes a problem is> within bracketed constructs in the handling of the terminal bracket,> the comma or the colon immediately after a terminal quote mark or> in dealing with an unquoted string.    I propose that within the> bracketed constructs _only_ we terminate the scan for a closing quote> delimiter on the combination of the quote delimiter followed by any of:> >      whitespace>      comma>      the closing bracket>      colon
Indeed, the delimited string terminated criteria can be easily updatedto handle ['one'','two''',three''''] style of strings without breakingCIF1 backwards compatibility.
Sincerely yours,Saulius
-- Dr. Saulius Gra┼żulisInstitute of Biotechnology, Graiciuno 8LT-02241 Vilnius, Lietuva (Lithuania)fax: (+370-5)-2602116 / phone (office): (+370-5)-2602556mobile: (+370-684)-49802, (+370-614)-36366_______________________________________________ddlm-group mailing listddlm-group@iucr.orghttp://scripts.iucr.org/mailman/listinfo/ddlm-group

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