Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ddlm-group] CIF2 semantics

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

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Council for Science (admitted 1947). Member of CODATA, the ICSU Committee on Data. Member of ICSTI, the International Council for Scientific and Technical Information. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

ICSU Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.