A few minutes ago I uploaded a version of my suggested revised proposal for UCDs to the Twiki. This is just a Word version since I don't have a PDF generator handy. The URL is
http://www.ivoa.net/internal/IVOA/IvoaUCD/UCD-1.9.9b.doc
This builds upon Roy and Sebastien's division of UCDs into concepts and propeties but puts them together rather differently.
In addition and largely independently, it includes a discussion of the use of UCDs in the context of groups of columns and tables as a whole. With the approach suggested, I hope that the ambiguities that have heretofore precluded considering using UCDs to mediate between data models and data can be removed and we may no longer require a utype parameter.
Some discussion of the document is included (in red) within the text. This mostly describes the relationship of this version to the 1.9.9 version.
Sections 3 and 6 of the document are copied from the previous version. (though section 6 was section 8 in that document) from the previous version. The abstract is altered to reflect the discussion of grouping constructs. Section 2 -- describing the status of the document -- has been changed to discuss the implications of the adoption of this recommendation upon existing software systems and protocols. I think that some such statement should be part of draft recommendations. Not sure if that's part of the recommendation process but it probably should be.
Section 4 is the discussion of UCDs and UCD syntax. At the end of section 4 there is a long parenthetical discussion of some of the ways this proposal differs from 1.9.9 since people seemed to be concerned about that last Thursday. If they've gotten this far they probably don't need this anymore but it may be of interest. This section tries to be rather rigorous -- addressing a fair number of nits that had not been talked about in the earlier proposal even though it makes the proposal somewhat longer (e.g., the discussion of array valued cells, a much more detailed discussion of comparability of columns, how to ensure the uniqueness of UCDs, ...)
The actual definition of all of the valid words for UCDs is deferred as it was in the earlier version, but a substantial number of examples are given. [In fact, most of the words should transfer between the two versions fairly transparently. The differences lie mostly in how they are put together.]
Section 5 is the dicussion of UCDs and grouping structures. I'm quite excited by this since I think it real potential for helping to unify discussions of data, data models and data access. The discussion in this chapter is less rigorous -- even if the basic idea is adopted I'm sure it will need substantially more work but I think it has real possibilities for linking data models and data. This chapter is why I've sent this message to the DAL and DM groups as well as to the UCD group. Apologies to all of you who get this twice or thrice!
I trust there will be comments...
Tom Received on 2003-10-21Z19:33:59