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

By 'systems' I had in mind computer operating systems and programming
environments, in particular multilingual support and Fortran.  So, for
example, as Herbert's replies have been indicating, Fortran behaviour
continues to influence the CIF standard.

On Thu, Oct 29, 2009 at 1:04 AM, David Brown <idbrown@mcmaster.ca> 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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