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Re: [ddlm-group] Role of separators in CIF
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] Role of separators in CIF
- From: Brian McMahon <bm@iucr.org>
- Date: Wed, 2 Dec 2009 15:29:09 +0000
- In-Reply-To: <C73C82E5.1274D%nick@csse.uwa.edu.au>
- References: <20091201105503.GE20378@emerald.iucr.org><C73C82E5.1274D%nick@csse.uwa.edu.au>
So I vote FOR James's proposition. Cheers Brian 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: >>> *NOTE REQUEST FOR VOTE BELOW* >>> >>> 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 > MBDP M002 > > CRICOS Provider Code: 00126G > e: Nick.Spadaccini@uwa.edu.au _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group
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