What is RDF?

The Resource Data Framework is a "graph" metadata format, meaning the data is expressed through a combination of several atoms of knowledge called "triples", each consisting of three pieces of information, a subject, an object, and a predicate linking these two. Each element of a triple is expressed through a URI. To give an example, a possible RDF triple encoding of the information "The Uni Dufour is in Geneva" could be the following:

<http://lod.unige.ch/uni-dufour> <http://lod.unige.ch/property/located-at> <http://lod.unige.ch/geneva>.

Each triple's object can be the subject from another triple and vice-versa. This allows knowledge graphs to be built from triples and especially  semantic knowledge to be added to the encoded data. In the previous example, it is for example possible to add semantic details on what kind of entity Geneva and Uni Dufour are by the means of new triples for each, Uni Dufour is a building while Geneva is a city. This is translated in RDF by the knowledge graph below:

Thanks to its semantic and flexible nature, RDF is a data format of choice for encoding more abstract real-life concepts, such as art acquisition, event unfolding, and historical document annotation.

RDF was also conceived as a data format for reconciling semantic entities with the "outside" world. The triples' URI encoding makes it easy to link resources external to the university, such as geographic locations referenced in geonames.org, renowned people listed in viaf.org, or any kind of entity both concrete and abstract catalogued in wikidata.org.

The hidden potential of such "bridges" to the outside world is truly realised through the use  of SPARQL queries, and more particularly Federated Queries, to simultaneously query the university's triplestore and a remote one. If the city of Geneva is referenced in an art history corpus as the home of an artwork, and its RDF entity is correctly reconciled to its wikidata equivalent, it is then possible to retrieve any relevant information recorded in wikidata under this entity, such as the date of the city's foundation or its population in 1914.