Benji York wrote: > Jean-Marc Orliaguet wrote: > >> the whole issue with RDF I think is: many who build representational >> models have noticed that the (subject, object, predicate) triad is not >> sufficiently flexible to represent knowledge that has to do with laws, >> agreements, abstract concept, regularity, phenomena that evolve with >> time, etc. > > > Can you give an example of one of these pieces of knowledge?
Yes: "John gives a book to Mary" means more than a dyadic relation followed by another: "John drops the book" and "Mary picks the book" it means that there is an agreement between John and Mary that the book is indefinitely hers (which '__ gives __ to ___' signifies). A notion of a transfer of the right of property, which no combination of dyadic predicates can express because all three elements in the relation must be taken in the same act. If you store the relations "John drops the book" and "Mary picks the book" how will you know if the book belongs to Mary and belonged to John before it was given to her? You could add "the book belongs to John" "the book belongs to Mary", add some date information, add the fact that the action is a gift (reification), ... all the pieces still have to be put together. This will need to be interpreted in a language (or a query language that does unions, intersections, ..) that knows how to put the pieces together. The model is very verbose is not explicit at all. "Joe prefers apples to cookies" cannot be expressed as a mere combination of: - "Joe likes apples" - "Joe likes cookies" - "apples are prefered to cookies" (i.e. by whom?) The last proposition is incorrect outside the context of "Joe prefering apples to cookies". So if you add such a relation to your storage without the context, you introduce a proposition that has no meaning. - a feedback loop is another one that cannot be expressed as a combination of dyads, since all 3 entities in the loop cooperate simultaneously. - zope adapters cannot be expressed by combining dyadic predicates only. When you look up an adapter you must pass the context AND the new interface. All three entities must be treated together. This could be a good exercice to convert the zcml declaration of adapters to a RDF schema and do something with it ... /JM _______________________________________________ Zope3-dev mailing list Zope3firstname.lastname@example.org Unsub: http://mail.zope.org/mailman/options/zope3-dev/archive%40mail-archive.com