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Re: CIF specification: reserved prefixes

I agree with Brian's suggestion -- we should ban underscores within
prefixes.  -- H. J. Bernstein


At 12:06 PM +0000 10/28/03, Brian McMahon wrote:
>Dear Colleagues
>
>While working through the content of International Tables Volume G, I have
>come upon two statements that are in flat contradiction. In the CIF
>specification, regarding the use of registered prefixes to reserve a
>namespace of data items for local use, it is stated:
>
>
>      \P 12. There is no syntactic property identifying such a reserved
>             prefix, so that software validating or otherwise handling
>             such local data names must scan the entire registry and
>             match registered prefixes against the indicated components
>             of data names. Note that reserved prefixes may themselves
>             contain underscore characters, so a maximal matching search
>             must be made.
>
>while in chapter 3.1, "General considerations when defining a CIF data
>item", I find I have written
>
>      3.1.2.2. Reserved prefixes
>
>      To guarantee that locally devised data names may be placed without
>      name conflict in interchange data files, authors may register a
>      reserved character string for their sole use. As with the special
>      prefix _[local]_ discussed in the preceding section, the author's
>      reserved prefix is simply an underscore-bounded string within the data
>      name (i.e. it may not itself include an underscore character).
>
>I can in fact see no useful purpose in permitting an underscore *within* a
>registered prefix - it simply complicates the task of the parser. At this
>stage no prefixes have been registered with an embedded underscore. I
>therefore propose to amend paragraph 12 of the CIF working spec, replacing
>the final sentence by
>
>      "Note that reserved prefixes may not themselves contain underscore
>       characters."
>
>Please let me have your opinions on this as quickly as possible. I shall
>continue to work on the Volume on the assumption that no objections will be
>raised to this amendment.
>
>Regards
>Brian
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>comcifs@iucr.org
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-- 
=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya@dowling.edu
=====================================================
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