Using Ontology Labels

Overview

Use ontology class and property labels in INSERT, MATCH, and REMOVE operations to leverage semantic capabilities.

Ontology Labels on Nodes

Use the @prefix:ClassName syntax to assign ontology class labels to nodes:

Syntax: :@prefix:ClassName in INSERT or MATCH patterns.

Insert node with ontology class label:

GQL
INSERT (:@foaf:Person {name: 'Alice', age: 30})

Insert node with multiple ontology labels:

GQL
INSERT (:@foaf:Person&@foaf:Agent {name: 'Bob'})

Create a path with ontology labels:

GQL
INSERT (:@ex:Person {name: 'Alice'})-[:@ex:knows]->(:@ex:Person {name: 'Bob'})

Ontology Labels on Edges

Edges can also have ontology labels using the @prefix:propertyName syntax. This enables domain/range validation and property characteristics like SYMMETRIC and TRANSITIVE.

Syntax: [:@prefix:propertyName] in edge patterns.

Insert edge with ontology label:

GQL
MATCH (a@ex:Person), (b@ex:Person)
WHERE a.name = 'Alice' AND b.name = 'Bob'
INSERT (a)-[:@ex:knows]->(b)

Match edges by ontology property:

GQL
MATCH (a)-[r:@ex:knows]->(b)
RETURN a.name, b.name

Edge with full IRI syntax:

GQL
MATCH (a)-[@<http://example.org/knows>]->(b)
RETURN a.name, b.name

Matching by Ontology Label

Use @prefix:name (without colon before @) to match nodes by their ontology class label:

Important: This matches the actual label assigned to the node.

Match nodes by ontology class:

GQL
MATCH (n@foaf:Person)
RETURN n.name

Subclass inference - Employee extends Person:

GQL
// Querying Person also returns Employee nodes
MATCH (n@ex:Person)
RETURN n.name, n.role

Match with both label and properties:

GQL
MATCH (n@ex:Person)
WHERE n.age > 25
RETURN n.name, n.age

IRI Matching (@= Syntax)

The @= syntax matches nodes by their _iri property value, NOT by their label. This is useful for finding specific individuals in semantic web data.

Key Distinction:

• @prefix:name - matches by label (ontology class)
• @=prefix:name - matches by _iri property value

Insert nodes with _iri property:

GQL
INSERT (:Person {name: 'Alice', _iri: 'http://example.org/alice'})
INSERT (:Person {name: 'Bob', _iri: 'http://example.org/bob'})

Match by IRI using prefix:

GQL
MATCH (n@=ex:alice)
RETURN n.name

Match by full IRI:

GQL
MATCH (n@=<http://example.org/bob>)
RETURN n.name

Label match vs IRI match:

GQL
// Given: (:@ex:Person {name: 'Alice', _iri: 'http://example.org/alice'})

// This matches by LABEL (ontology class)
MATCH (n@ex:Person) RETURN n.name  // Returns Alice

// This matches by _iri PROPERTY
MATCH (n@=ex:alice) RETURN n.name  // Returns Alice

// These are DIFFERENT - one checks label, one checks _iri property

Removing Ontology Labels

Use the REMOVE clause to remove ontology labels from nodes. The node itself remains; only the label is removed.

Syntax: REMOVE variable@prefix:ClassName

Remove ontology label from a node:

GQL
MATCH (n@foaf:Person)
WHERE n.name = 'Alice'
REMOVE n@foaf:Person

Verify label was removed:

GQL
// This now returns empty - Alice no longer has the label
MATCH (n@foaf:Person)
WHERE n.name = 'Alice'
RETURN n

Node still exists with its properties:

GQL
MATCH (n)
WHERE n.name = 'Alice'
RETURN n.name, n.age

Combining Labels

You can combine regular labels, ontology labels, and IRI matching using & (conjunction) and | (disjunction).

Combine regular label with IRI match:

GQL
MATCH (n:Person&@=ex:alice)
RETURN n.name

Multiple ontology labels:

GQL
MATCH (n@foaf:Person&@foaf:Agent)
RETURN n.name

Insert with regular and ontology labels:

GQL
INSERT (:Employee&@ex:Person {name: 'Carol', role: 'Developer'})