The Web Ontology Language (OWL) is a family of knowledge representation languages for authoring ontologies. Ontologies are a formal way to describe taxonomies and classification networks, essentially defining the structure of knowledge for various domains.
OWL adds more vocabulary for describing properties and classes than basic RDF schema, including relations between classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.
In this wiki, OWL is used by the reasoning engine in the Wiki CLI to perform deductive expansion of your graph (e.g., using OWL-RL rules).
Defining custom RDFS/OWL axioms
Custom reasoning rules and class hierarchies can be declared natively in file Frontmatter or standalone .ttl imports. The reasoning engine automatically scans the combined pool.
To define a hierarchy such that TechArticle is a specialized subset of schema:CreativeWork, you can declare it directly in the ontology:
# wiki/tech-article.md
---
id: wiki:TechArticle
type: owl:Class
rdfs:subClassOf: schema:CreativeWork
---
Deductive reasoning consequences
Under OWL-RL reasoning rules, when you have a page:
type: TechArticle
name: Learning SPARQL
The reasoning engine automatically infers and adds the following facts to your graph:
- The page is also a
schema:CreativeWork.
Related
- Graph Cache — inference defaults and graph reuse
- Wiki Subcommand query —
--no-inference - Wiki Subcommand serve —
inference=query parameter - RDF