The learning path
Eight modules, in order. Each links to the precise definitions and the primary sources.
What an ontology actually is
The canonical definition and how it evolved — from Gruber's “explicit specification of a conceptualization” (1993) to Studer's “formal, explicit specification of a shared conceptualization” (1998) and Guarino's logical-theory view.
Read the definitions →The anatomy: classes, properties, instances
The building blocks. Classes (concepts), the properties that describe and relate them (slots), the restrictions on those properties (facets), and the individuals that populate them — the vocabulary from Noy & McGuinness.
See the glossary →The languages: RDF, RDFS, OWL, SKOS
How ontologies are actually written down. The triple model (RDF), the schema vocabulary (RDFS), the full ontology language (OWL 2), and the lighter-weight standard for taxonomies (SKOS) — all W3C standards.
Learn the standards →Reasoning: description logic & inference
Why an ontology is more than a schema: it's a logical theory a machine can reason over. Description logic, the TBox/ABox split, the open-world assumption, and what a reasoner actually computes.
Understand reasoning →How to build one: the 7-step method
The practical process from Noy & McGuinness's Ontology Development 101 — determine scope, reuse, enumerate terms, define classes, properties, facets, and instances. Iterative, with competency questions as the test.
Read: Build an Ontology →Foundations: upper ontologies
The abstract scaffolding everything else hangs from — BFO, DOLCE, SUMO. Why a foundational ontology matters, and how it makes independent ontologies interoperable.
See the definitions →Reuse: don't reinvent the wheel
Most domains are already modeled. How to find an existing ontology, judge its fit, reuse the terms you need (MIREOT), and enhance it — instead of building from scratch.
Read: The Ontology Already Exists →The ground truth: primary sources
Every claim on these pages traces to a citation. The foundational papers and the W3C specifications — including Ontology Development 101 as a downloadable PDF.
Open the references →