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Re: [ddlm-group] Objectives of CIF2 syntax discussion. .
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] Objectives of CIF2 syntax discussion. .
- From: David Brown <idbrown@mcmaster.ca>
- Date: Wed, 19 Jan 2011 14:26:28 -0500
- In-Reply-To: <alpine.BSF.2.00.1101191234221.42382@epsilon.pair.com>
- References: <AANLkTikZoEF_D+5-3+Eg4pbCx0cAu+SJvR-a_XkC3zK2@mail.gmail.com> <alpine.BSF.2.00.1101190833560.91751@epsilon.pair.com> <8F77913624F7524AACD2A92EAF3BFA54166D7D1ECE@SJMEMXMBS11.stjude.sjcrh.local> <alpine.BSF.2.00.1101191042290.42382@epsilon.pair.com> <4D371BE7.3050501@mcmaster.ca><alpine.BSF.2.00.1101191234221.42382@epsilon.pair.com>
Dear Herbert, I suggested earlier that we could easily add the style tag you suggest. In some cases where an earlier dataname has already been superceded by a second dataname it would be necessary to indicate which is the proper (i.e., later) name that should be used on writing since all datanames that have ever been approved must appear in the alias list. With the style tag the _alias_uri would not be as important and could be omitted. There are a number of reasons why your import scheme would have made life considerably more complicated. The first is that the old tags do not conform to CIF2 syntax and therefore would have to be insulated within the routines that manipulates the data under DDLm CIF-dictionary control. The second is that DDLm has a much tighter heirarchical category structure that is desinged to simplify the merging and updating of the dictionaries. This was introduced to overcome some of the weaknesses of the earlier file structures. Allowing the DDL1 and DDL2 datanames to be defined in save frames within the DDLm dictionary would lead to incompatibilities that would prevent many of the newly introduced features in DDLm being used. For example in DDLm the category and object parts of the datanames are defined independently and represent the two components out of which the dataname is constructed at run time. The dataname in the save_ statement is, by convention, a composite of these two components, but it is not the definition of the name. Since it is not possible with the older datanames to separate them into a catagory and object component without in some cases misnaming the category, their presence would effectively mean that the tighter features of DDLm could not be used either in programming or in updating and merging. One should not try to put new wine into old wine skins. Anyway it sounds as if we have agreement on at least something. and knowing that DDLm can achieve compatibility with the earlier archive by using the aliases on reading and writing, and proper DDLm names otherwise, should simplify the discussions on syntax. Herbert J. Bernstein wrote: Dear David, |
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