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[ddlm-group] CIF2 summary?
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: [ddlm-group] CIF2 summary?
- From: Joe Krahn <krahn@niehs.nih.gov>
- Date: Wed, 04 Nov 2009 20:00:47 -0500
Is there a summary of the CIF2 syntax somewhere, or is it still just an ongoing discussion? My understanding so far is: HEADER: The "magic" initial comment "#CIF2" is required. LISTS: Item lists within braces (aka curly brackets) and delimited by commas. There is more than one use of the list syntax, but all types of lists probably have a common parsing syntax. I assume that quoting rules are the same for normal item values, and that commas and braces must all be contained in quotes. Can a list contain semicolon delimited strings? Also, how is the use of comma delimiting within a list advantageous? Wouldn't the STAR2 syntax be easier, where tokenizing values within a list is identical to tokenizing outside of the list? UTF-8: Support for UTF-8 characters. Is this only for strings, and possibly comments, or can data names have UTF-8 as well? Are there any plans in the DDL to restrict where UTF-8 can be used? Eventually, it might be nice to put Greek letters in atom names, but most software assumes ASCII. TRIPLE QUOTES: Triple double-quotes can be used to delimit single or multiple line strings. They can contain any printable characters except for a triple-quote that is not immediately preceded by '\'. Can the triple-quote strings contain non-printable chars, i.e. for efficient binary encoding? If so, is NUL allowed? UNQUOTED CHARACTERS: More restrictions on characters allowed in unquoted strings. I am mostly guessing here: Unquoted strings cannot contain anywhere in the string: curly brackets, square brackets, or quote characters followed by non-whitespace. Are the characters '$' and '#' disallowed anywhere, or just at the beginning? QUOTED STRINGS: In quoted strings, a matching quote character followed by non-whitespace still count as a quote, unless preceded by '\'. Otherwise, it is a syntax error, because whitespace is required between strings. _______________________________________________ ddlm-group mailing list ddlm-group@iucr.org http://scripts.iucr.org/mailman/listinfo/ddlm-group
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