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First Ontology

This guide walks through building a small ontology with the builder API — no repository clone required.

Prerequisites

  • Rust 1.88+ (rustc --version must be >= 1.88.0)

Unfamiliar with OWL terms (TBox, ABox, materialization)? See the Glossary.

Classification: see Rust integration contract.

Step by step (crates.io)

use ontologos_core::{Error, Ontology};

fn main() -> Result<(), Error> {
    // 1. Register entities and axioms via the builder
    let ontology = Ontology::builder()
        .class("http://example.org/Pizza")?
        .class("http://example.org/Food")?
        .subclass_of("http://example.org/Pizza", "http://example.org/Food")?
        .build()?;

    // 2. Query the taxonomy index
    let pizza = ontology
        .lookup_entity("http://example.org/Pizza")
        .expect("registered");
    let supers = ontology.direct_superclasses(pizza);
    assert_eq!(supers.len(), 1);

    // 3. Round-trip through JSON (v3 writer on v1.0.0; v2 still readable)
    let json = ontology.to_json()?;
    let restored = Ontology::from_json(&json)?;
    assert_eq!(restored, ontology);

    Ok(())
}

ABox axioms

The builder supports named individuals and ABox assertions:

use ontologos_core::{Error, Ontology};

fn main() -> Result<(), Error> {
    let ontology = Ontology::builder()
        .class("http://example.org/Person")?
        .individual("http://example.org/alice")?
        .object_property("http://example.org/knows")?
        .individual("http://example.org/bob")?
        .class_assertion("http://example.org/alice", "http://example.org/Person")?
        .object_property_assertion(
            "http://example.org/alice",
            "http://example.org/knows",
            "http://example.org/bob",
        )?
        .same_individual(&[
            "http://example.org/alice",
            "http://example.org/alice-copy",
        ])?
        .different_individuals(&[
            "http://example.org/alice",
            "http://example.org/bob",
        ])?
        .build()?;

    let alice = ontology
        .lookup_entity("http://example.org/alice")
        .expect("alice");
    let person = ontology
        .lookup_entity("http://example.org/Person")
        .expect("person");
    assert_eq!(ontology.individuals_of(person), &[alice]);

    Ok(())
}

Additional builder methods: equivalent_object_properties, asymmetric_object_property, property_domain, property_range, subproperty_of.

After building an RL-shaped ontology, saturate with OWL RL saturation.

Optional: repository example (clone required)

From a clone:

cargo run -p ontologos-core --example pizza_builder

Next steps