- From: Richard Cyganiak <richard.cyganiak@deri.org>
- Date: Thu, 12 Aug 2010 13:59:30 +0100
- To: Mark Birbeck <mark.birbeck@webbackplane.com>
- Cc: Ivan Herman <ivan@w3.org>, public-rdfa-wg@w3.org
Mark, You are arguing that something that can obviously be done in practice actually is completely impossible in theory. I will now pay the RDF Tax and waste an hour of my life to show you that what is possible in practice, is of course possible in theory as well, you just need to do some mental gymnastics to get RDF Semantics to play along. On 12 Aug 2010, at 11:55, Mark Birbeck wrote: > if I make a statement about > <http://purl.org/dc/terms/> I am making statements about the /entity/ > this URI refers to. The URI is the name for the entity, and it's not > possible to say anything about the /name/ in RDF (i.e., about the > URI). > > For this reason, the following technique is a non-starter: > > <http://xmlns.com/foaf/0.1/name> rdfa:term "blabla" . > > The desire is to make a statement about a string of text that can be > substituted during RDFa parsing, but this statement doesn't do that; > instead it is making a statement about the *entity represented by the > URI*. No matter which way we twist and turn, it is not possible to do > anything otherwise in RDF. I can parse the RDF statement above using my library of choice, and run the following SPARQL query over it: SELECT ?uri WHERE { ?uri rdfa:term "blabla" } The answer will be <http://xmlns.com/foaf/0.1/name>. And this is all that is needed, end of story. Now your argument is that the library didn't return a string but a URI, which is just a reference to some entity in the world. And hence I am not allowed to do stringy things with the returned URI. While the first part is true, I really don't get where you get that second part from. > * in RDF you can't saying anything about the lexical form of a URI; Where in RDF Semantics does it say please that the universe excludes the URIs of things? I demand a quote. If there's no such restriction in the spec, then I can use RDF to say things about URIs. Example. In the world of RDF Semantics, URIs are identifiers for entities. So let X be the relationship that holds between an entity and the number of characters of a URI that identifies this entity. Furthermore, let foo:uriLength be an identifier for this relationship X. Now this is a trivially true statement: <http://xmlns.com/foaf/0.1/name> foo:uriLength 30 . While we have no evidence for the following statements (and hence can conclude they are false under closed-world reasoning): <http://xmlns.com/foaf/0.1/name> foo:uriLength 29 . <http://xmlns.com/foaf/0.1/name> foo:uriLength 31 . Look, I'm making statements about the lexical form of a URI. > * any properties we add to a URI concern the entity that URI > represents, and not the string of characters itself; That is correct, but consistent with my proposed definition of rdfa:term. In RDF Semantics language, rdfa:term identifies the binary relationship that holds between an entity and a short form for the URI of that entity. Best, Richard > * I think you should stick to your pedantry, Ivan! ;) > > Regards, > > Mark > > -- > Mark Birbeck, webBackplane > > mark.birbeck@webBackplane.com > > http://webBackplane.com/mark-birbeck > > webBackplane is a trading name of Backplane Ltd. (company number > 05972288, registered office: 2nd Floor, 69/85 Tabernacle Street, > London, EC2A 4RR) -- Linked Data Technologist • Linked Data Research Centre Digital Enterprise Research Institute (DERI), NUI Galway, Ireland http://linkeddata.deri.ie/ skype:richard.cyganiak tel:+353-91-49-5711
Received on Thursday, 12 August 2010 13:00:06 UTC