Types

TypeQL is a polymorphic query language that supports strong typing and uses types defined in the schema of a database to construct queries to the database.

Type hierarchy

Types are defined in the schema of a database, and their definitions are written in TypeQL. Types from the schema are used to design data queries to the database and are modeled with the use of the PERA model. Type definitions can be used in Define and Undefine queries and can’t use any variables.

To create new types in a schema, subtype one of the existing types. A subtype inherits all definitions of its supertype.

By default, a schema has three built-in root types. Root types are abstract types and need to be subtyped to use them.

Table 1. Root types
Root type label	A subtype of the root type	A data instance of a subtype
`entity`	Entity type	Entity
`relation`	Relation type	Relation
`attribute`	Attribute type	Attribute

Since data instances can be named after their respective root type, we try to prevent ambiguity by specifying whether we mean the root type or data instance in every case if it’s not obvious from the context.

Abstract types

Abstract types can’t be used to insert data instances, but can be subtyped and queried for.

To make a type abstract, use the abstract keyword in its definition.

Abstract type definition example

define

subject sub entity, abstract;

Usage in a Define query

Let’s define a simple schema for users:

Define query example

define

id sub attribute, value long;
email sub attribute, value string;
full-name sub attribute, value string;

user sub entity,
    owns id @key,
    owns email,
    abstract;

person sub user, owns full-name;

Usage in a Fetch query

Now let’s fetch all types from the database:

Fetch query example

match
$x sub! $y;
fetch
$x;

This simple pattern lets us match all types from a database:

Output

{ "x": { "label": "user", "root": "entity" } }
{ "x": { "label": "entity", "root": "entity" } }
{ "x": { "label": "attribute", "root": "attribute", "value_type": "object" } }
{ "x": { "label": "relation", "root": "relation" } }
{ "x": { "label": "person", "root": "entity" } }
{ "x": { "label": "email", "root": "attribute", "value_type": "string" } }
{ "x": { "label": "full-name", "root": "attribute", "value_type": "string" } }
{ "x": { "label": "id", "root": "attribute", "value_type": "long" } }

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