[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: A certain difficulty
David Megginson wrote: > Mark Birbeck <Mark.Birbeck@i...> writes: > > Of course we could say everyone must use "dc:Creator", but then how > > do I find everyone who ever knitted a jumper? Well of course I go to > > the knitting site that has used RDF to refer to subsets of other > > data, because they have a class called "Knitter". > > Take a look at the class. Consider the following: > > <rdf:RDF ...> > > <megg:Jumper rdf:about="http://www.foo.com/1"> > <dc:creator rdf:about="http://www.people.org/a"/> > </megg:Jumper> > > <megg:Book rdf:about="http://www.amazon.com/ids/00002"> > <dc:creator rdf:about="http://www.people.org/b"/> > </megg:Book> > > </rdf:RDF> > > If you want to find every knitter but not every author, then simply > look only for dc:creator properties attached to an object of class > megg:Jumper. The alternative is to create an endless stream of new > properties > > create > sweaterCreator > bookCreator > carCreator > webPageCreator > cartoonCreator > flyingSaucerCreator > emailCreator > badSmellCreator > > etc. Of course, you have no choice but to do this kind of thing when > you're using flat HTML <meta> tags, but RDF was designed specifically > to allow you to apply modern OO techniques to the problem. I must say I prefer old-fashioned OO techniques then ;-) where I'm not limited to only having one class. Why in your model have you decided that 'creator' is the must use tag for anyone who creates something, but 'hook' and 'jumper' are valid objects? If your argument was consistent then you should just have a generic object that can be a person, book or jumper, and a 'created by' tag. And then I can say 'this jumper was created by that book' which we may want to inhibit. Which is the nub of my criticism of this 'one schema fits all' stuff. It just doesn't cut it. I am suggesting that the preferred model is to say that 'author' and 'knitter' are sub-classes of 'creator'. Then if you want all creators you can find them, and if you want all authors you can find them. But more than that, you can say that the 'creator' of a 'book' must be an 'author', and not a 'car' or 'elephant'. Another problem with your example is that you're dealing with instances of the class and not the class itself. I might not have any information in my database about books that you have written David, but I could still use RDFS to find out that you are an author. With the example you gave above, I would only know that you are an author if I have a book in my database. What do you think? Best regards, Mark *************************************************************************** This is xml-dev, the mailing list for XML developers. To unsubscribe, mailto:majordomo@x...&BODY=unsubscribe%20xml-dev List archives are available at http://xml.org/archives/xml-dev/threads.html ***************************************************************************
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