CIF specification: reserved prefixes
Brian McMahon bm at iucr.orgTue Oct 28 12:06:15 GMT 2003
- Previous message: New version (2.3) of core CIF dictionary available
- Next message: CIF specification: reserved prefixes
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
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
- Previous message: New version (2.3) of core CIF dictionary available
- Next message: CIF specification: reserved prefixes
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
More information about the comcifs mailing list