I think Drupal 7 stands a chance of being a killer semantic app, it’s the next version of a CMS with a sizeable install base and when the release is final and everyone starts upgrading suddenly tons of sites will be automatically exposing RDF in the form of embedded RDFa without any intervention on the … Read more
The first two of these, DatatypeProperty and ObjectProperty, describe what kind of values a triple with the property should have. Datatype properties relate individuals to literal data (e.g., strings, numbers, datetimes, etc.) whereas object properties relate individuals to other individuals. Something like hasAge would typically be a datatype property, since an age is a number, … Read more
Basic definitions RDF is a concept. RDF is also a NAME of a vocabulary. RDFS is a NAME of another vocabulary. “ontology” is just a SYNONYM of the term “vocabulary”. Explanations RDF is a concept RDF is a concept or a way of describing things. The concept of RDF is that you are describing / … Read more
Gephi was already mentioned, but I’ll incode screenshots and a short description here. Gephi can not just visualize graphs but also supports analyzing, layouting and further importing and exporting. There is a Semantic Web Import Extension that allows you to directly query (via SPARQL) or import RDF data. https://wiki.gephi.org/index.php/SemanticWebImport (You can install it directly within … Read more
From a simplistic point of view, the domain and range properties are there to give you insight into the way that the property links a subject to an object. In the case of the domain property, when you link a subject to an object using a property with this associated attribute, then the subject qualifies … Read more
The best explanation is by example. Try googling for all cars advertised on the web with engines smaller than 2.0 litres that run unleaded, and have an mp3 connection and can been seen in a showroom conveniently accessible by public transport from my house. Google just won’t be able to help you with that query, … Read more
*Edit, May 2015: Times have changed… again. Schema.org seems the way to go, using either microdata (W3C note) or RDFa (W3C recommendation), where the RDFa Lite variant is easiest to learn. Meanwhile recently Microformats released a new version as well, which nobody is paying attention to currently. Also see the answer to What is the … Read more
Well, the obvious first start is to look at the classes and properties present in the data. Here is how to see what classes are being used: SELECT DISTINCT ?class WHERE { ?s a ?class . } LIMIT 25 OFFSET 0 (LIMIT and OFFSET are there for paging. It is worth getting used to these … Read more
The semantic web comes in layers. This is a quick summary of the ones I think you’re interested in. Update: Please note that RDFS is used to define the structure of the data, not OWL. OWL describes semantic relationships which normal programming, such as a C struct, isn’t fussed about and is closer to AI … Read more