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Draft CIF2 standard available

  • Subject: Draft CIF2 standard available
  • From: James Hester <jamesrhester@xxxxxxxxx>
  • Date: Fri, 12 Mar 2010 11:43:59 +1100
Dear CIF developers,

As some of you may be aware, a new CIF dictionary framework is under
development.   This framework consists of an updated CIF syntax
(CIF2), a new set of dictionary attributes (DDLm), and a
machine-readable language for describing algorithmic relationships
between datanames (dREL).  The working group for developing this new
framework has come up with a final draft for the CIF2 syntax
component, which is available at
http://www.iucr.org/__data/assets/pdf_file/0005/40775/syntaxchangesproposed20100218.pdf.
 We are now seeking feedback from the community on this proposed new
syntax standard.  Please note that this CIF2 standard is designed to
coexist with the CIF1 standard (which it closely resembles), rather
than to replace it.

The discussions surrounding the CIF2 specification are archived at
http://www.iucr.org/__data/iucr/lists/ddlm-group/ .

Some highlights of the the proposed CIF2 syntax:

* A list datavalue is introduced: lists are enclosed by square
brackets, e.g. [1 2 3 4] or  [[1 'x'] 3 ['y' 5 ['pqr' 7] 8 ]].
List-valued data items are vital for economically expressing matrix
and vector relationships in dREL algorithms.

* A table datavalue is introduced, enclosed by curly braces, e.g.
{"colour":"red" "size":"really big"}.  Table datastructures allow
tabulated values (e.g. f' values) to be transparently accessed in dREL
algorithms.

* Both lists and tables are recursive, that is, lists and tables can
contain other lists and tables

* Multi-line strings may now be delimited using triple quotes (""") or
triple single quotes ('''), as well as the CIF1.1 <newline><semicolon>
delimiter.

* Single-quote delimited strings and double-quote delimited strings
may not contain instances of the delimiter character.  This differs
from the CIF1.1 standard, which allowed instances of the delimiting
character if the next character was not whitespace.

* CIF2 files are in UTF8 encoding.  Note that ASCII is a proper subset of UTF8.

The DDLm working group would welcome any feedback you may have on this
specification, whether through open discussion on this list or by
contacting members of the working group (see the online discussion
archive for names of the participants).

James Hester
COMCIFS chair
--
T +61 (02) 9717 9907
F +61 (02) 9717 3145
M +61 (04) 0249 4148
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