As some of you may know, I've been following the Semantic Web stuff quite closely over the last month or so, and I'm in the planning stages of building the Semantic Outlining framework so that you can add RDF triples to outline elements in OPML 2.0. 
I’ve been playing around with Protege in order to try and understand RDF Schemas and OWL. It seems simple enough, but it doesn’t really do what I need, which is allow me to assert equivalence.
So, if I come up with some schema or namespace for terms - and start using those as predicates, is there any way of asserting that when I define myschema:title, it’s the same as dc:title?
Nova Spivack has written about this problem:
One of the reasons for this is that each ontology has it’s own naming conventions, philosophical orientation, domain nuances, design biases and tradeoffs, often guided by particular people and needs that drove their creation. Integrating across these different worldviews and underlying constraints is often hard.
The dream of the Semantic Web vision is that someday there will be thousands or millions of ontologies around the web, and millions of instances of them. And these will all somehow be integrated automagically, or at least if they aren’t integrated on the semantic level, then there will be magic software that embodies that integration… Unless mappings are created between [ontologies], instead of a Semantic Web, we’ll just have millions of little semantic silos. Maybe some company will succed in making the biggest silo and that will be “the” semantic web to most people. That might be the best solution in fact, but I’m not sure that is really what Tim Berners-Lee had in mind!
It’s great that we’ve got things like SPARQL, but unless we come up with some kind of way of mapping together distinct ontologies, then I fail to see the point in actually carrying on developing ontologies and churning out RDF.
Can’t we just extend the schema/ontology languages - RDFS, OWL etc. - so as to define equivalence? I mean, if you churn out RDF in one way, I could write a schema (or copyright concerns aside, copy a pre-existing schema) and add some extra assertions to it to express equivalence.
So, we’d have triples that are like this:
http://rdf.opiumfield.com/example/title isEquivalentTo http://purl.org/dc/elements/1.1/title .
http://rdf.opiumfield.com/example/author isEquivalentTo http://purl.org/dc/elements/1.1/creator .
As for inferring other schematic ‘stuff’ like the required conditions or disjoints, well, that is a challenge, but surely getting a globally compatible semantic system working comes before defining dis-relationships.
To think that we’re going to get one absolute, set schema is poppy-cock. Or, as Cory Doctorow would say, it’s metacrap. In the OPML space, distributed directories are an example of where competition should happen - if you think that you can run the root node better than the current root node maintainer, fire up your outliner and give it a try. Surely, we need similar competition in the semantic space?
Update: I’m still hoping that someone can give me more information, but I’m presuming that owl:sameAs serves this function. I really need to get my head around OWL properly, but it seems pretty damn confusing.
Surely, on the Semantic Web, the value is the person who builds pipes between the formerly siloed data, no? That’s what I’m looking for - and I’m not sure whether owl:sameAs does that or not.
Tag: rdf, semanticweb, owl, rdfs, protege, schema, semweb, opml, semanticoutlining
