Class Definitions

Overview

Define ontology classes to categorize nodes with semantic meaning. Classes support inheritance hierarchies and can be marked as disjoint.

Creating Classes

Define a new ontology class:

GQL
CREATE CLASS @ex:Person

Create a class with description:

GQL
CREATE CLASS @ex:Employee DESCRIPTION 'A person who works for an organization'

Create multiple related classes:

GQL
CREATE CLASS @ex:Person
CREATE CLASS @ex:Organization
CREATE CLASS @ex:Location

Class Hierarchy (EXTENDS)

Create subclasses using EXTENDS to define inheritance:

GQL
// Person is a subclass of Agent
CREATE CLASS @foaf:Agent
CREATE CLASS @foaf:Person EXTENDS @foaf:Agent
CREATE CLASS @foaf:Organization EXTENDS @foaf:Agent

GQL
// Employee extends Person
CREATE CLASS @ex:Person
CREATE CLASS @ex:Employee EXTENDS @ex:Person
CREATE CLASS @ex:Manager EXTENDS @ex:Employee

Subclass Inference

When you query for a superclass, nodes with subclass labels are automatically included:

GQL
// Insert an Employee (which extends Person)
INSERT (:@ex:Employee {name: 'Alice', role: 'Engineer'})

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

GQL
// Query specifically for Employee
MATCH (n@ex:Employee)
RETURN n.name, n.role

Disjoint Classes

Mark classes as mutually exclusive - a node cannot have labels from both:

GQL
CREATE CLASS @ex:Cat
CREATE CLASS @ex:Dog DISJOINT WITH @ex:Cat

Attempting to create a node with both labels will fail in STRICT enforcement mode:

GQL
// This fails: Cannot be both Cat and Dog
INSERT (:@ex:Cat&@ex:Dog {name: 'Mystery'})
// Error: Disjoint class violation

Multiple disjoint declarations:

GQL
CREATE CLASS @ex:Mammal
CREATE CLASS @ex:Bird DISJOINT WITH @ex:Mammal
CREATE CLASS @ex:Fish DISJOINT WITH @ex:Mammal, @ex:Bird

Viewing Classes

List all defined classes:

GQL
SHOW CLASSES

Deleting Classes

Remove a class definition:

GQL
DROP CLASS @ex:TempClass

Remove if exists (no error if class doesn't exist):

GQL
DROP CLASS IF EXISTS @ex:TempClass