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Revised CIF syntax guidelines
- To: "Discussion list of the IUCr Committee for the Maintenance of the CIFStandard (COMCIFS)" <comcifs@iucr.org>
- Subject: Revised CIF syntax guidelines
- From: James Hester <jamesrhester@gmail.com>
- Date: Thu, 31 Mar 2011 15:20:57 +1100
Dear COMCIFS, Please find below a slightly revised version of the guidelines for developing base CIF syntax and semantics. I have taken the version most recently posted by John Bollinger, and following discussion with John Westbrook, have added a couple of points relating to maintaining compatibility with previous versions of CIF (1 (vi) and (vii)). Note also that I have also adjusted the text in 1 (ii) to refer to scientific domains in which CIF is used, rather than scientific domains in general. I plan to call a vote on accepting these guidelines following a short further period for discussion of the revision below. ============================================== Principles guiding development of Base CIF 2.0 ---------------------------------------------------------------------- Preamble CIF is a framework for exchanging and archiving scientific data, featuring a human-readable, machine-parseable, file format designed to serve as an exchange and archive medium. 'Base' CIF comprises the definitions and constraints that underlie CIF and apply to all CIF files; those aspects defining the CIF file format are documented in the CIF Syntax specification and the CIF Common Semantic Features specification. Base CIF aims to remain as simple as possible by delegating considerations such as ontology, vocabulary, data relationships, and complex and rich data types to domain dictionaries and the DDL formalisms by which those dictionaries are defined. In the following, the phrase 'domain level' refers to such documents (though it is anticipated that only dictionaries, not DDLs, will be domain-specific). Definitions and constraints at domain level apply to a particular CIF file only as declared by that file or as required by a particular CIF processor in a particular context. Principles The design of base CIF 2.0 is guided by these principles: 1. A feature should be added to or changed in base CIF only if all of the following are satisfied: (i) Implementation of the desired behavior by changes at the domain level is not feasible, or else such changes, while feasible, would significantly reduce human readability; (ii) the change provides significant new functionality that is widely applicable to those scientific domains where CIF is used (iii) reliable transfer and archiving of data is not compromised (iv) there is no simpler way of achieving the desired behaviour (v) it has been shown possible to implement the change at a cost commensurate with its benefits, as demonstrated in part by a rough consensus and running code. (vi) Where possible, any new CIF syntax features should be developed as an extension to the current standard, and thus not change the interpretation of archival files that conform with previous versions of the CIF standard. (vii) Where it is impractical to provide for full backward compatibility as described in (vi), the relevant archival repositories and software developers should be consulted to arrive at a solution that will minimize the impact of such changes. 2. As long as the requirements in (1) are satisfied, base CIF should: (i) behave in a way that is consistent with common usage (ii) align with pre-existing standards where those standards provide the required behaviour. CIF 1.1 can be considered a pre-existing standard for CIF 2.0 in this context. 3. Non-technical issues should be dealt with in non-technical arenas. 4. Draft changes to base CIF will be made available on the IUCr website for public comment for a period of at least 6 weeks, following which COMCIFS voting members, after consideration of any objections raised, can vote to accept the change. A change will be accepted if 3/4 of COMCIFS voting members approve it. =============== -- T +61 (02) 9717 9907 F +61 (02) 9717 3145 M +61 (04) 0249 4148
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