Thoughts on some of the parts of RDF family - RDF, RDFS, OWL and applications such as OWL DL, DC, RSS 1.0, Adobe XMP and how they relate.
The "semantic web stack" as typically seen in Tim Berners-Lee's talks is as follows ("top"-down):
- Web Ontology Language (OWL)
- RDF Vocabulary Description Language (RDF Schema)
- Resource Description Framework (RDF)
This means that:
- OWL adds functionality to RDF VDL:Schema
- RDF VDL:Schema adds to RDF
however, all RDF is OWL, all RDF is RDFS
I've simplified the above, since OWL (formally, OWL Full) has some varieties or flavours. OWL DL is the OWL vocabulary for reasoners, a profile of OWL. OWL Lite is a smaller subset of that and I've even seen "OWL Feather" mentioned a few times - not a formal subset. None of these are on the stack directly but relate "upwards" to OWL [Full].
There are other applications nearby that relate in various ways.
The Dublin Core Metadata Element Set (DCMES) is (or rather, has) an RDF vocabulary and the most widely used. [Hopefully we'll get a bit of OWL in here too]
CC/PP is a vocabulary/ontology based on RDF
Adobe XMP is a profile of RDF both graph and RDF/XML syntax - some graphs won't fit in the syntax or have to be present. Some things cannot be present.
RSS 1.0 is an ontology or vocabulary adding functionality to RDF. It also restricts the graph by defining how the RDF/XML is allowed.