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Re: [ddlm-group] A modest addition to the DDLm spec. .
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] A modest addition to the DDLm spec. .
- From: Nick Spadaccini <nick@csse.uwa.edu.au>
- Date: Fri, 01 Oct 2010 13:37:27 +0800
- In-Reply-To: <alpine.BSF.2.00.1009302249150.70666@epsilon.pair.com>
On 1/10/10 10:54 AM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com> wrote: > Dear Nic, > > If the spec is quoted string literal + quoted string litera;, > +4 is no problem, it is just +4. Unfortunately this means that a + can't be a legitimate unquoted string in the presence of quoted strings, but can be if NOT in the presence of quoted strings. This surely has to be confusing. Example loop_ atom_site.id atom_site.charge_sign atom_site.atom_type "C123" + "C" would return C123C plus an error for the missing data values for the last two items. At a lexical level "C123" + "C" is different to "C123" + C and different to C123 + C. Since people use quoted and unquoted strings interchangeably I fear this will give rise to ambiguity. Of course if you do away completely with unquoted strings (I have argued this) the problem disappears. If all strings have to be quoted then the symbol + will have a completely unique interpretation. > "breaking the underlying structure of a > tag-value construct in the original STAR/CIF" is no more done > by this extension than it was by the bracketed constructs. This is a little disingenuous. The bracketed constructs were extensions to make the representation more powerful. It actually didn't break the underlying structure, since [string] was already allowed in the syntax. It merely made the interpretation of the contents more in line with expectation. The PDB had littered its data with [1,2,3] (no spaces) as unquoted strings expressly representing lists. We just formalised it. However single tag - single value is the definition of the STAR/CIF syntax. The new formalism does break that. But this is all moot. CIF2 is developing in a very different direction to STAR and is no longer a subset. It is in some ways and an extension in many others. DDLm can be extended to incorporate some of the changes to definition language, but there are syntax variations that cannot. The same with dREL where quite different language extensions need to be incorporated. CIF2 is developing its very own syntactic definitions, its own DDL and supporting scripting language, all of which can be based on STAR, DDLm and dREL, yet very different. The DDLm and dREL syntax and examples Syd and I issued for consideration provides a good basis for this group to move forward. I am under pressure from Syd to finalise the STAR, DDLm and dREL we implemented in to journal papers - which I will do. I am under more pressure from my Faculty in different directions. Time is short and my contribution to CIF2 discussions is at best minimal, and of late non-existent. Good luck with these developments and I hope to see applications in the near future that exploit its possibilities. 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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