Re: Discussion list of the IUCr Commission on CrystallographicComputing

[David Brown <idbrown@mcmaster.ca>]

For the Osaka Computing School I would like to suggest a further topic 
which is tentatively entitled:

               Programming for CIF and related file structures.

While the format of CIF is familiar to most crystallographers, 
programming for CIF is only now taking advantage of the unique features 
that CIF offers, namely the machine-readability of CIF dictionaries.  
This allows browsing and editing programs to obtain all their 
crystallographic knowledge from the CIF dictionaries.  A single program 
can therefore read any type of CIF and it does not have to be rewritten 
every time a new version of the CIF dictionary is released.  We have 
recently seen programs, such as publCIF and enCIFer, that adopt this 
approach.  More recently PyCIFRW, written by James Hester, not only 
validates a CIF against its CIF dictionary, but can validate the 
dictionary against the Dictionary Definition Languare (DDL, the 
dictionary's dictionary), a great assistance to people constructiong CIF 
dictionaries.  A new generation of programmers is arising who are 
interested in exploiting all the possibilities built into the CIF 
standard. 

In the fifteen years since CIF was adopted by the IUCr, the weaknesses 
of the early version of the standard have become obvious, particularly 
the unfortunate development of two incompatible CIF standards: CIF1 used 
for small-cell crystallography and CIF2 for macromolecules.  To adddress 
these weaknesses COMCIFS has approved the development of an advanced 
dictionary language, tentatively called DDLm, which will be used to 
create CIFm dictionaries that are fully backwardly compatible with both 
CIF1 and CIF2.  Most importantly CIFm dictionaries will include methods: 
computer-readable algorithms that allow derived items, such as the 
density, to be calculated directly from other items present in the CIF.  
Because DDLm should be ready for approval by the end of this year and 
work will then start on preparing CIFm dictionaries and software, the 
Osaka School occurs at just the right time to present CIFm to our keen 
young programmers. 

CIFm is being designed for maximum compatibility with XML.  However, it 
will not make CIF1 and CIF2 obsolete.  Indeed programs designed to use 
CIFm dictionaries will be able to apply the advanced features to any 
CIFs in the existing archive.  CIFm will add value, but not replace CIF1 
and CIF2; the present CIF standards and software will continue in use 
for as long as people wish to use them. 


begin:vcard
fn:I.David Brown
n:Brown;I.David
org:McMaster University;Brockhouse Institute for Materials Research
adr:;;King St. W;Hamilton;Ontario;L8S 4M1;Canada
email;internet:idbrown@mcmaster.ca
title:Professor Emeritus
tel;work:+905 525 9140 x 24710
tel;fax:+905 521 2773
version:2.1
end:vcard

_______________________________________________
compcomm mailing list
compcomm@iucr.org
http://scripts.iucr.org/mailman/listinfo/compcomm