Java Glossary : RDF

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Resource Development Framework. A proposed W3C standard to allow you to embed computer-comprehensible data in your HTML documents. The key is encoding data with standard tag dictionaries called ontologies. It would allow a search engine for example to distinguish between Whirlpool appliances and natural whirlpools. RDF evolved from XML and hence shares its fluffiness. It would allow a software agent to make reservations for you on many airlines since the airlines would present the essential information embedded in the HTML in a computer-friendly way using a standard vocabulary/ontology.

Facts are encoded as triples:

a URI (something that can be named uniquely, e.g. a webpage location, a book title via ISBN).
A property name such as surname, phoneNumber.
A value, either a literal or a pointer to where the information can be found, e.g. the surname or the phoneNumber.

Attempting to encode all knowledge using just proper nouns and attribute values leaves a lot out, but at least it is a start at making the Internet more accessible to software agents.

In the XML representation, the properties may manifest as either tags or attributes just to keep you on your toes.

There are many competing ontologies and ontology schemas. I gather the hope is it will eventually narrow down to a few ontologies in each field and that someone will figure out how to make them interoperable. Ontology schemes such as DAML+OIL also allow you to describe logical relations, e.g. who eats who in a ontology of animals and plants. Another is OWL.

The other thing RDF tackles is the issue of trust. Who said such and such a fact was so. It uses digital signatures.

RDF provides FOAF with a way to mix together different descriptive vocabularies in a consistent way. Vocabularies can be created by different communites and groups as appropriate and mixed together as required, without needing any centralised agreement on how terms from different vocabularies should be written down in the XML.

digital signatures ¤ FOAF ¤ XML

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