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Regarding numbers, could Herbert or others who wish 4.5 and "4.5" to have different abstract types , whereas kkkkk and "kkkkk" have the same abstract type, please explain why this behaviour is preferable, how it allows useful work to be done etc. Meanwhile I'll prepare a post describing my reasoning for more uniform behaviour.
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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: James Hester <jamesrhester@gmail.com>
- Date: Tue, 26 Jul 2011 23:24:15 +1000
- In-Reply-To: <a06240802ca545e68933f@192.168.2.101>
- References: <CAM+dB2eL5jrEFBcmGpDe6RTvpv4qfmxXa722XXzaS_zgCjsxKw@mail.gmail.com><a06240802ca545e68933f@192.168.2.101>
Regarding numbers, could Herbert or others who wish 4.5 and "4.5" to have different abstract types , whereas kkkkk and "kkkkk" have the same abstract type, please explain why this behaviour is preferable, how it allows useful work to be done etc. Meanwhile I'll prepare a post describing my reasoning for more uniform behaviour.
On Tue, Jul 26, 2011 at 10:13 PM, Herbert J. Bernstein <yaya@bernstein-plus-sons.com> wrote:
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.
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--
=====================================================
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
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