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Re: Revised statement of policy on CIF

While Syd and Herbert's discussion is interesting, it does little to
address the point raised by Brian.

The key is in the phrase 'CIF syntax'.  A program that reads a CIF does
not need to know about any datanames that it does not need, so that as
long as it can recognise that any string starting with an underline is a
dataname, and as long as it can navigate its way around loops and save
frames, it should be compliant and able to read CIFs using both DDL1 and
DDL2 dictionaries.  It may not be able to retrieve the particular
information it is looking for because the CIF uses a dataname for the same
information taken from a later version of the dictionary, but the program
should still terminate successfully. To deal with this latter situation,
the author of the program may wish to indicate the dictionary and version
used in the software, but this would be only for the benefit of the
user.  It does not prevent the program from reading the CIF.

Similarly, a program that writes a CIF will write it using a particular
dictionary, be it one using DDL1 or DDL2.  In either case it will have
written a conforming CIF (if it has done the job correctly) i.e.,
a CIF that can be read by a conforming read program.  That is the extent
of the compliance that we require.

I am not sure why Howard is concerned.  The information in a CIF
downloaded from the IUCr web page contains information for which a
non-exclusive copyright has been assigned to the IUCr.  The copyright
owners are the author and the Union in right of Acta Cryst.  The Union may
be granting free license to use the CIF language, but it is not giving
away any rights it has to the information content of the file.  These are
explicitly reserved to the author or the author's assignees whose identity
is clear.  However, Herbert's addition would be a wise clarification.


Dr.I.David Brown,  Professor Emeritus
Brockhouse Institute for Materials Research, 
McMaster University, Hamilton, Ontario, Canada
Tel: 1-(905)-525-9140 ext 24710
Fax: 1-(905)-521-2773