Comments on Utypes note

(http://www.ivoa.net/internal/IVOA/Utypes/WD-Utypes-0.3-20090522.pdf)

@2.1 "data model elements": need to agree what these may be. That is need to know the syntax of data modelling. When in UML this might mean deciding on using Class diagrams. Or choosing a particular UML profile. Or possibly a custom language defined for "data modelling in the VO". This is what we have done in SimDB and therefore we were able to define ("BNF") and implement (XSLT) rules for deriving Utypes from the data model.

Semantics of UTYPEs

If a column in a table is declared to have a particular Utype it is possible to assume that that column stores a value that has been obtained from the corresponding attribute in an "exact instance" of the data model.

How about the table containing that column though. If it is given a utype corresponding to a Class in the model, how is it related to an exact instance to that class? Should it be an exact representation? Should it contain columns for all attributes and references?

Possible use cases:

  • Annotation for results of ADQL queries on SimDB/TAP
  • annotating element in TAP_SCHEMA representation of SimDB/DM
  • annotating elements in XML schema representation of SimDB/DM
  • Identification of elements in models derived from SimDB/DM, for example in views.
  • ...

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Topic revision: r5 - 2009-06-15 - GerardLemson
 
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