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Re: CIF development

  • Subject: Re: CIF development
  • From: Brian McMahon <bm@xxxxxxxx>
  • Date: Mon, 8 May 2000 14:00:04 +0100 (BST)
Richard 

> Brian, at the present time it appears that only one dictionary can be
> associated with a given data block. Is that the case? If so then do all the
> deprecated names have to live in a separate block linked to others via the
> _audit_link_ mechanism?

That's NOT the case. Dictionaries are associated with a data block through
the AUDIT_CONFORM category, which can be looped. The example in the CIF Core
dictionary has a single linkage, but an extended example suitable for a
powder CIF could be

data_powder_dataset
  loop_ 
     _audit_conform_dict_name
     _audit_conform_dict_version
     _audit_conform_dict_location
        cif_core.dic      2.1      ftp://ftp.iucr.org/pub/cif_core.2.1.dic
        cif_pd.dic        1.0      ftp://ftp.iucr.org/pub/cif_pd.dic

> Along these lines I'd like to see (in a library of dictionary
> access/manipulation tools) a routine that'll return the "new" name for a
> deprecated dataname (and probably vice-versa). Simple pointers could be
> present in the main dictionary so specialty dictionaries could be
> loaded/searched for full validation but simple old-to-new name mapping should
> be able to be handled using only one dictionary.

The promised dictionary protocol will explain how to construct a single
compound dictionary from a collection of smaller dictionaries or fragments.
It will also outline a versioning protocol so that a clever validator can
download and then cache the latest version of the dictionary. Indeed, it may
be the case in the future, if enormous numbers of data names are defined,
that individual definitions are requested from a dictionary serversolely
according to need.

If you want to look through the draft proposal, there's a copy at
http://www.iucr.org/iucr-top/lists/comcifs-l/msg00048.html, although take
care: it may change in the next couple of weeks before I formally release
it to this list.

Regards
Brian


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