- From: Pat Hayes <phayes@ihmc.us>
- Date: Fri, 28 Oct 2011 00:20:59 -0500
- To: Heiko Paulheim <paulheim@ke.tu-darmstadt.de>
- Cc: semantic-web@w3.org
On Oct 27, 2011, at 10:17 AM, Heiko Paulheim wrote: > Dear RDF experts, > > I have a question concerning the equivalence of rdf:Bags. Given the following RDF/XML document: > > <?xml version="1.0"?> > <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> > <rdf:Bag rdf:about="http://foo.bar/myBooks"> > <rdf:li rdf:resource="http://foo.bar/ABook"/> > <rdf:li rdf:resource="http://foo.bar/AnotherBook"/> > </rdf:Bag> > </rdf:RDF> > > Converting it to triples using the W3C RDF validator [1] yields > > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#_1 http://foo.bar/ABook > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#_2 http://foo.bar/AnotherBook > > Now, switching the order of the two <rdf:li ...> elements and running the validator again yields > > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#_1 http://foo.bar/AnotherBook > http://foo.bar/myBooks http://www.w3.org/1999/02/22-rdf-syntax-ns#_2 http://foo.bar/ABook > > As far as I understand the graph equality definition given at [2], these two graphs are different, assuming that rdf#_1 and rdf#_2 are two different predicates. How does that go together with the idea that an rdf:Bag is unordered? The graphs are different. However, the bags being described by the graphs might not be; they certainly contain the same elements, in any case. The numbers in the property names _1, _2, etc. should not be interpreted as imposing an order on the elements. They do in a seq, but not in a bag. But RDF only describes seqs and bags, it does not actually construct them. Pat Hayes > > I am sure that I am missing a trivial point here, so I would be happy if someone could give me a hint. > > Best regards, > Heiko. > > [1] http://www.w3.org/RDF/Validator/ > [2] http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-graph-equality > > ------------------------------------------------------------ IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Friday, 28 October 2011 05:21:40 UTC