OWL: Ontologies and Reasoning

Resources

Specs

• W3C OWL 2 Overview - Maps the OWL 2 document suite and explains the three profiles (EL, QL, RL) which trade expressiveness for computational tractability.
• W3C OWL 2 Primer - Gentle intro with examples. Covers classes, properties, restrictions, and reasoning.

Books

• Semantic Web for the Working Ontologist (Allemang & Hendler) - The practical guide. Covers RDF, RDFS, OWL, and SPARQL with a focus on building real ontologies.
• A Semantic Web Primer (Antoniou & van Harmelen) - More academic. Good for understanding the theoretical foundations.

Others

• W3C OWL Guide (OWL 1) - Older but still the most comprehensive walkthrough with wine ontology examples.
• Manchester Pizza Ontology Tutorial - Hands-on: Build an ontology from scratch using Protege. The de facto “hello world” for OWL.

In Semantic Web

• OWL ontologies enable the automatic inference discussed in The Graph Space. Property graphs have no equivalent, reasoning must be custom code.

RDFS vs OWL

RDFS (RDF Schema) and OWL are both for defining vocabularies, but at different levels:

• RDFS: Lightweight. Classes, subclasses, domain/range of properties. Enough for simple taxonomies.
• OWL: Full reasoning. Cardinality constraints, transitive/symmetric properties, equivalence, disjointness. Needed when you want machines to infer new facts.

Most real-world ontologies use a mix: RDFS for the basics, OWL where inference is needed.