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I agree with Mike.  Having said that, I believe that UML is more useful for defining the second sort of data model than the first.  In ISO/IEC JTC 1/SC 32/WG 2 (Metadata), UML is very heavily used to define models of (and metamodels for) metadata.  These models (and metamodels) are the second sort of data model, IMHO.

By contrast, in ISO/IEC JTC 1/SC 32/WG 3 (Database languages), UML is not used at all.  That's because the SQL data model is quite close to the relational model of data.  From an application point of view (e.g., a manufacturing company), the relational model and/or SQL data model are "metamodels" that provide standardized syntax and data structures that the application uses to define the user's business data model.

Hope this helps,

On 2016-09-27 05:41, Michael Kay wrote:

As I look through the XML Schema specification I see no UML diagrams.


As I look through the GML specification I see many UML diagrams.


Are UML diagrams not relevant/useful for data models in the first sense? Are UML diagrams only relevant/useful for data models in the second sense?


I suspect that the kind of people who define models like the XML schema model and the relational model are more comfortable with maths and legalese English than with pictures. So I think it tells you more about the psychology of the individuals concerned than anything else.

Michael Kay

Jim Melton --- Editor of ISO/IEC 9075-* (SQL)     Phone: +1.801.942.0144
  Chair, ISO/IEC JTC1/SC32 and W3C XML Query WG    Fax : +1.801.942.3345
Oracle Corporation        Oracle Email: jim dot melton at oracle dot com
1930 Viscounti Drive      Alternate email: jim dot melton at acm dot org
Sandy, UT 84093-1063 USA  Personal email: SheltieJim at xmission dot com
=  Facts are facts.   But any opinions expressed are the opinions      =
=  only of myself and may or may not reflect the opinions of anybody   =
=  else with whom I may or may not have discussed the issues at hand.  =

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