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Re: [ddlm-group] CIF2 semantics
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] CIF2 semantics
- From: "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
- Date: Tue, 26 Jul 2011 08:13:14 -0400
- In-Reply-To: <CAM+dB2eL5jrEFBcmGpDe6RTvpv4qfmxXa722XXzaS_zgCjsxKw@mail.gmail.com>
- References: <CAM+dB2eL5jrEFBcmGpDe6RTvpv4qfmxXa722XXzaS_zgCjsxKw@mail.gmail.com>
On null values, I believe "." and "?" are different in meaning from their unquoted versions, but that unquoted . and ? are both essentially equivalent null values. On numbers, past practice has been to treat 4.5 and "4.5" as very different, the former being a type numb value and the latter being a type char value. This was an important and significant early difference between CIF and STAR and has been used in the handling of the number-like strings that arise in PDB bib entries, e.g. 1234-5678 is the number 1234e-5678, but "1234-5678" is a string At 1:24 PM +1000 7/26/11, James Hester wrote: >Dear DDLm group, > >In order to minimise the number of issues we have to discuss in >Madrid to clean up CIF2, I would like to turn discussion to those >semantic issues which are relevant to the syntax. I believe that >there are three possible types of datavalue: "inapplicable", >"unknown" and "string", represented by <full point> (commonly called >a "full stop" or "period"), <question mark> and everything else, >respectively. > >Do we all agree with the following assertion regarding full point >and question mark? >(1) A full point/question mark inside string delimiters is *not* >equivalent to an undelimited full point/question mark > >Numbers: I believe that strings that could be interpreted as numbers >are nevertheless (in a formal sense) just strings in the context of >the post-parse abstract data model. Therefore, whether or not a >numerical string is delimited does not change its value: 4.5 and >"4.5" are identical values. > >Note that this latter assertion does *not* require that >CIF-conformant software must always handle numbers as strings; I am >making these statements in order to clarify the abstract data model >on which the various DDLs and domain dictionaries operate, not to >dictate software design. If your software can manage any potential >need to swap between string and number representation of your data >value, then more power to you. > >Please state whether you agree or disagree with the above. > >James. >-- >T +61 (02) 9717 9907 >F +61 (02) 9717 3145 >M +61 (04) 0249 4148 > >_______________________________________________ >ddlm-group mailing list >ddlm-group@iucr.org >http://scripts.iucr.org/mailman/listinfo/ddlm-group -- ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group
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