[Cif2-encoding] Splitting of imgCIF and other sub-topics. .... .. .

[Bollinger, John C]

Hi Brian,

On Thursday, September 16, 2010 8:18 AM, you wrote:
[...]
>I favour the specification *recommending* a magic string to begin a
>file: an optional BOM followed by the 11 characters
>
>#\#CIF_2.0<whitespace>

Can you expand on that a bit?  Ignoring all considerations of character encoding, CIF 2.0 syntax is not 100% backwards compatible with CIF 1 syntax.  (Handling of quoted strings is the most prominent area of incompatibility, but there are others.)  If a CIF processor is presented with a file having no version identification comment, then which syntax would you want it to assume?

[...]

>These are recommendations, not requirements,
>
>1. to include existing CIF1.0 and CIF1.1 instances as valid CIF input
>streams (whether "decorated" or not;

Making the version comment optional in CIF2, as you suggest, would make *most* well-formed CIF1 instances also be well-formed CIF2 instances -- but not all of them.  Making CIF2 accommodate all of CIF1 would require substantial changes to those parts of the draft that we have considered settled.  Is it that important to you?


Thanks,

John
--
John C. Bollinger, Ph.D.
Department of Structural Biology
St. Jude Children's Research Hospital


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