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Re: [ddlm-group] THREAD 3: The alphabet of non-delimited strings.

This would seem to create a serious divergence between valid DDLm CIFs and
valid DDL1 and DDL2 CIFs.  I would suggest putting this specific proposal
out to the wider community for comments.  Up until now we had been trying
to assure people that the change to DDLm would not invalidate existing
CIFS.  I for one would hope we could do something less drastic.
   -- Herbert

  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769


On Fri, 18 Sep 2009, Nick Spadaccini wrote:

> As I have written before, non-delimited string (non-DS) that are not of the
> Number or Measured types cause problems. Everything you need to include in a
> string can be handled by the delimited string types. With the introduction
> of compound data structures, restrictions have to be imposed on the allowed
> alphabet of non-delimited strings so the scanner is not "fooled".
> If you HAVE to use non-delimited strings then the alphabet is restricted to,
> non-DS = [A_Za-z0-9./-()+?][A_Za-z0-9_./-()+?]*
> (Allowing for / is in deference to James, I don't see a great need for it.)
> The square brackets [] are part of the regexp and not allowed characters.
> This will cover all numerics including Measured, and decline the first
> character as _. None of the token delimiters are included in the alphabet.
> Note also the classic example of symop is x,y+1/2,z IS NOT allowed, though a
> quick scan of the IUCr cif archive shows many submissions already quite
> sensibly use "x,y+1/2,z".
> One level of simplification will be in the definition of datanames (DN). We
> could simply define a data name as
> DN = _{non-DS}
> All CIF data names in the new DDLm dictionaries are consistent with this
> restriction. A small amount of remediation (which has to be undertaken
> anyway) will need to be done for existing domain dictionaries written in
> either DDL1 or DDL2.
> A further simplification is that one can write the scanner to look for token
> terminating characters, rather than DEMANDING it be followed or preceded by
> a whitespace.
> cheers
> Nick
> --------------------------------
> Associate Professor N. Spadaccini, PhD
> School of Computer Science & Software Engineering
> The University of Western Australia    t: +61 (0)8 6488 3452
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