Gregor's wrote: "That may be an excellent idea indeed. But then we should call it a "tag" and not "category" or "class", and make clear that adding multiple tags will remain uninterpretable - other than as you indicated."
Eamonn wrote: I don't really mind what we call our terms but if they are coming from a non-hierarchical, controlled vocabulary (a class?) (http://rs.tdwg.org/ontology/voc/SPMInfoItems.rdf) don't we leave open the possibility that these may eventually be arranged into an OWL ontology?
I did not mean that, I meant that if *two* tags are added, that the relation of these tags should not be interpreted other than indicated by you. If two terms are added, one provider may intend a union, another an intersection, another a specification of the first by the second. I think we should make a recommendation that SPM is not meant to allow this interpretation detail.
What you say is that one could introduce a new term "ecological genetics" and then define it to be the intersection of ecology and genetics, using OWL statements. I believe you can not define in OWL how the repeated occurrence of a single attribute "Tag" with two values shall be interpreted semantically, right?
Gregor