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Re: [ddlm-group] Relationship of CIF2 to legacy platforms

Dear Colleagues,

   It would be a shame if the adoption of CIF2 cut off use of CIF by purely 
Fortran applications, such as XDS.  The would cement the highly negative
impression of CIF in the macromolecular community.

   At present, for CIF to be supportable from purely Fortran applications, 
it is essential to have an upper limit on the length of lines, and to
include trailing blank stripping in the specification.  There is, at 
present, no portable way to delect the length of an input line in 
fortran nor to deal with lines the maximumum length of which is not
known in advance.  The current CIF 1 limit of 2048 characters could
be extended, but not to infinity, as you can for use with C.


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


On Wed, 28 Oct 2009, David Brown wrote:

> James asks whether we should require CIF2 to support legacy systems.  I am 
> not sure what James means by 'systems'.  Are these datafiles or programs? 
> That is to say is the queston 'should CIF2 applications be able to read 
> legacy CIFs?', or 'should legacy CIF1 programs be able to read CIF2 
> datafiles?'? 
> The answer to the first question is definitely 'yes'.  It is part of the 
> mandate of CIF2 that its programs should be able to process the existing 
> archive so that the archive can take advantage of the enhanced functions of 
> DDLm.  The CIF2 dictionaries will alias all the datanames appearing in the 
> CIF1 dictionaries in a way that makes such reading easy.
> The answer to the second question is almost certainly no, at least in cases 
> where the CIF data file makes use of the added syntax features.  All the 
> datanames in CIF1.0 dictionaries differ from those in the CIF2 dictionary by 
> not using a period at the end of the category part of the name and in some 
> cases the names differ in other ways.  There would be no point in trying to 
> produce CIF2 compatible CIF1 dictionaries, since the CIF1 dictionaries are 
> poorly designed for maintenance and have poor aliasing features.
> David
> James Hester wrote:
>> Dear All,
>> I think it would be helpful to make a policy decision regarding our
>> treatment of legacy systems in CIF2.0.  This concerns first and
>> foremost Fortran derived line-length constraints, but may impact on
>> the encoding discussion in deciding which encodings might get some
>> special treatment.  There may be other such issues as well.
>> We have a few choices:
>> 1. Disregard legacy system issues when designing CIF2, on the basis
>> that such systems can continue to use CIF1 and will eventually
>> disappear at about the same time that it does (sort of like ASCII and
>> Fortran...)
>> 2. Continue to support legacy systems on the basis that we don't want
>> to deny such systems the chance to partake of the raw unadulterated
>> goodness of CIF2, or perhaps more seriously that such legacy systems
>> are integral to CIF2 takeup.
>> What do you think?
>> James.
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