[Tdwg-tag] UML limitations for our uses?

Roger Hyam roger at tdwg.org
Mon Apr 3 14:03:59 CEST 2006

There is an interesting article here:


That discusses the differences between OWL and UML.

One of the features of OWL that I like is the notion of a necessary and 
sufficient properties but alas this is lacking in UML. Sufficient 
conditions allow you to determine if an instance is a member of a class 
when it in not explicitly stated. You can therefore receive and object 
and work out what it is according to an ontology of your choice - which 
seems pretty useful to me. It is a mechanism, I believed, could enable 
us to integrate a simple core ontology with more complex specialist 
ontologies that some network participants may choose to use. It is not 
available in UML but could be used to reason about a UML ontology 
expressed in OWL or RDFS.

OWL doesn't do qualified cardinality restrictions as well as UML - but 
there are work rounds and proposals and I am not sure how important this is.

There is also a good quote in the article on data modeling versus 
building ontologies:

"A data model is a model of the information in some restricted 
well-delimited application domain, whereas an ontology is intended to 
provide a set of shared concepts for multiple users and applications. To 
put it simply: data models live in a relatively small closed world; 
ontologies are meant for an open, distributed world (hence their 
importance for the Web)."

I think we are sometime confusing the two in our discussions.

Bottom line is:

    * You can't express everything in UML or OWL.
    * If we want to assure that we can swap between two or more modeling
      languages then we can't use all the feature of any of them but
      have to come up with a subset.

The answer never includes a single TLA. <- apart from this answer!

My personal feeling is that anything that is defined centrally by TDWG 
should use the lowest common denominator of features anyhow.

As usual I am grateful for you comments/thoughts.



 Roger Hyam
 Technical Architect
 Taxonomic Databases Working Group
 roger at tdwg.org
 +44 1578 722782

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