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Re: [ddlm-group] Role of separators in CIF

So I vote FOR James's proposition.


On Wed, Dec 02, 2009 at 08:47:33PM +0800, Nick Spadaccini wrote:
> msg00038 correctly states that the restriction of the character set for
> non-delimited strings is non-negotiable if we are to adopt the features of
> DDLm. That is a restriction the syntax has to be in place for delimited
> lists and tables to be possible.
> At the time (some two messages prior) the restriction I proposed was
> everything except for alphnumeric ascii and a few punctuation characters
> (because it was tightly aligned to the restrictions on characters for
> datanames). By the time that thread gets to msg00099 the restriction is only
> a few punctuation characters. Clearly people understood the
> non-negotiability had to do with the requirement of a restriction, but that
> the character set was negotiable - otherwise the 61 messages between
> msg00038 and msg00099 shouldn't have been possible.
> The restriction I proposed in msg00099 was all the terminator characters
> plus the token separators for lists and tables (those at that time, they
> have since evolved). The use of terminators in non-delimited strings can
> cause problems, especially when viewed or they are ambiguous. Can I
> construct lexing rules such that " and ' can be included in a non-delimited
> string so that is not be ambiguous or result in error - like Simon I suspect
> yes, I haven't thought of an example that systematically fails.
> Do I think it is sensible to restrict the terminator characters and
> separators except for two? No. I think a consistent rule that terminators
> and separators are All disallowed makes more sense and easier to articulate.
> For example the two cases below would be non-delimited strings.
> _quote   ."Hello"
> _quote ``Hello''
> However it would seem only JW and I have this point of view. So cast your
> final votes and lets get on with it. I think this will finish finally the
> syntactic issues.
> For the record (I think) the restriction I propose would be
> " ' : { } [ ] # commas are now returned to the allowed list
> Or if you vote "for", the restriction is
> : { } [ ]
> Nick
> On 1/12/09 6:55 PM, "Brian McMahon" <bm@iucr.org> wrote:
>> I want to vote "For" on this proposition, but I'm concerned by Nick's
>> assertion of 9 October
>> http://www.iucr.org/__data/iucr/lists/ddlm-group/msg00038.html
>>      (1) restricting the character set of non-delimited strings is
>>      NON-NEGOTIABLE. If we don't restrict it, then we can't build
>>      recursive data structures and exploit DDLm.
>> I understood this to be definitely ruling out the embedding of the
>> quote characters in non-delimited strings, but I've lost track of the
>> details of the subsequent discussions.
>> Regards
>> Brian
>> On Tue, Dec 01, 2009 at 04:56:52PM +1100, James Hester wrote:
>>> Simon: From reading your previous emails, I'm guessing that the source of
>>> your concern is that the possible characterset of non-delimited strings
>>> appears more restrictive than is strictly necessary.  In particular, you're
>>> not sure why we have excluded quote and double quote from non-delimited
>>> strings.
>>> You are correct that the other CIF2 syntax does not require that quote or
>>> double quote are excluded from non-delimited strings (apart from the first
>>> character, of course).  The exclusion of the quote/double quote was on
>>> general principle of keeping all characters that serve as delimiters out of
>>> non-delimited strings, even if those characters could never cause confusion.
>>> It also has the benefit of allowing some syntax errors to be picked up.
>>> Nick is with me in Sydney, and we have decided that this is the sort of
>>> issue that we just have to vote on, as the arguments either way are not
>>> conclusive.
>>> I would therefore call everybody to vote on the following proposition:
>>> "That <quote> and <double quote> may appear in non-delimited strings, as
>>> long as they are not the first character"
>>> Voting so far:
>>> Against: Nick
>>> For: James
>>> Agnostic: ?
>>> -- 
> 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
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