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Re: [ddlm-group] CIF-2 changes

Dear Colleagues,

   We have now come full circle with no agreement on anything.  I for one,
for the reasons outlined in many prior messages, do not think this
latest (=oldest) approach to be a good idea.

   Clearly, if we are ever to resolve this, we need to get all the players
into a meeting at one time and work things out.  I suspect we will not be 
able to arrange a timely physical meeting.  Perhaps some sort of an
emeeting (Ajax, Skype or somesuch) would work.


  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769


On Tue, 17 Nov 2009, Nick Spadaccini wrote:

> Davidąs Option 3 is the simplest way forward, and actually revisits much of
> what was discussed back in 2007-08. Somehow those discussions were locked
> far back in my brain, only to be awakened by Davidąs summary. Thanks for
> that.
> So now I return to the STAR syntax. DDLm is part of STAR and hence
> restrictions on data names so they can be parsed etc is a STAR issue. I am
> brought around to Joeąs idea that STAR accepts any 8 bit character sequence
> since that is the most complete set ­ and that this will be restricted to
> UTF-8 within the CIF specification. Any other adoptee of STAR can choose
> whatever restricted encoding they wish.
> I still need to treat data names as programming identifiers within dREL so
> accordingly I propose we restrict the data names in STAR (and all variants)
> to be ASCII [A-Za-z0-9_.] as we have used in the sample dictionaries, DDLm
> and dREL.
> The data values will be represented as discussed in previous threads and
> that the reverse solidus and the token delimiters discussed will be ASCII
> characters. We can now return to [] as the list delimiters, and {} as the
> associative array delimiters.
> Backward compatibility to CIF1 names is handled by exploiting the _alias
> attributes in the definition. A CIF2 parser with dictionary can handle
> everything. Any CIF1 parser can handle CIF1 data files (also CIF2 data files
> up to a point, but wonąt know what the data names mean ­ unless they have
> hardcoded it).
> A CIF2 parser would like a leading comment to tell it what sort of file it
> is parsing. It the absence of that comment, a pre-scan will need to be done.
> The telltale indicators it is a CIF1 data file are multiple occurrences of,
> (1) data names that potentially contain [] or /
> (2) unquoted strings with illegal characters
> (3) quoted strings that result in parse failure (typically because they must
> have an embedded [but not elided] quote character as allowed in CIF1).
> It needs to be a pre-scan because all 3 of the above in an identified CIF2
> data file would result in something quite different since there are coercion
> rules for when the whitespace separator is missing.
> For instance IF I KNOW it is a CIF2 file and I read
> _name[1]
> Then this can only be an error and I coerce into
> _name   [1]
> IF I DONąT KNOW the file type, the occurrence of _name[1] flags it as
> potentially a CIF1 file. If _name[1] is in an alias list, this re-enforces
> the likelihood of CIF1. Multiple instances of these łerrors˛ (or any others
> in the above list) indicate it is a CIF1 file (my only other conclusion
> would be it is a VERY BADLY written CIF2).
> I think this takes us back to a very simple rule set, and I donąt think the
> restriction in the character set for data names will cause problems. For all
> the excitement of UTF-8 etc I know of programming languages that support
> reading and writing data in such encodings but I havenąt seen one that
> allows/encourages one to write programmes declaring identifiers in UTF-8
> character sets. (They well exist I just havenąt seen them).
> On 17/11/09 12:04 AM, "David Brown" <idbrown@mcmaster.ca> wrote:
>> James,
>> There seems to be a lull in the discussions on CIF2 syntax so this would be a
>> good time for you, or appointed chosen by you, to summarize where we are at
>> and propose a set of rules that will can work with as we move forward.  I
>> realize that much of the work I have already done on dictionaries will need to
>> be revisited, and Herbert also seems anxious to have some decisions on the
>> various topics that have been discussed.
>> I believe we have a consensus on a number of points, but these need to be
>> written down clearly and need our formal agreement so we can move ahead.
>> David
>> _______________________________________________
>> ddlm-group mailing list
>> ddlm-group@iucr.org
>> http://scripts.iucr.org/mailman/listinfo/ddlm-group
> cheers
> Nick
> --------------------------------
> Associate Professor N. Spadaccini, PhD
> School of Computer Science & Software Engineering
> The University of Western Australia    t: +61 (0)8 6488 3452
> 35 Stirling Highway                    f: +61 (0)8 6488 1089
> CRAWLEY, Perth,  WA  6009 AUSTRALIA   w3: www.csse.uwa.edu.au/~nick
> MBDP  M002
> CRICOS Provider Code: 00126G
> e: Nick.Spadaccini@uwa.edu.au
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