Ontology

Overview

GQLDB supports ontology features that bring semantic web capabilities to your graph database. This allows you to define classes, properties with domain/range constraints, and enable inference based on class hierarchies.

Key Concepts:

Classes - Define types for nodes with inheritance (EXTENDS) and exclusivity (DISJOINT)
Object Properties - Define edge types with domain/range constraints and characteristics (SYMMETRIC, TRANSITIVE)
Data Properties - Define typed properties on nodes with XSD types
Prefixes - Shorthand for IRI namespaces (like foaf: for FOAF vocabulary)
Inference - Automatic classification based on class hierarchies

LPG vs Ontology Graph

Feature	LPG (Labeled Property Graph)	Ontology Graph
Node labels	Free-form labels	Ontology class labels (@prefix:Class)
Edge types	Free-form types	Object properties with domain/range
Schema	Optional (open graph) or defined (closed graph)	Class and property definitions
Inference	None	Subclass inference, property characteristics
Validation	Type checking only	Domain, range, cardinality, disjoint checks

Creating an Ontology Graph

Create a graph with ontology support enabled:

GQL
CREATE GRAPH my_ontology_graph ONTOLOGY

Loading Prefixes

Prefixes provide shorthand for IRI namespaces. Load common vocabularies:

GQL
// Load common prefixes
LOAD PREFIX foaf FROM 'http://xmlns.com/foaf/0.1/'
LOAD PREFIX ex FROM 'http://example.org/'
LOAD PREFIX rdfs FROM 'http://www.w3.org/2000/01/rdf-schema#'

View loaded prefixes:

GQL
SHOW PREFIXES

prefix	iri
foaf	http://xmlns.com/foaf/0.1/
ex	http://example.org/
rdfs	http://www.w3.org/2000/01/rdf-schema#

Loading External Ontologies

Import ontology definitions from OWL/RDF files:

GQL
// Load FOAF ontology from URL
LOAD ONTOLOGY FROM 'http://xmlns.com/foaf/spec/index.rdf'

GQL
// Load from local file
LOAD ONTOLOGY FROM 'file:///path/to/my-ontology.owl'

GQL
// Load with specific format
LOAD ONTOLOGY FROM 'http://example.org/onto.ttl' FORMAT 'turtle'

Viewing Ontology Information

View defined classes:

GQL
SHOW CLASSES

class	superclass	description
@foaf:Person	@foaf:Agent	A person
@foaf:Organization	@foaf:Agent	An organization
@ex:Employee	@foaf:Person	An employee

View defined properties:

GQL
SHOW PROPERTIES

property	type	domain	range	characteristics
@foaf:knows	OBJECT	@foaf:Person	@foaf:Person	SYMMETRIC
@ex:worksFor	OBJECT	@foaf:Person	@foaf:Organization
@foaf:name	DATA	@foaf:Agent	xsd:string

See the following pages for detailed information: