Closed Graph

Overview

The closed graph is constrained by its graph type, which imposes a strict framework that governs data insertion: each node or edge belongs to exactly one pre-defined node type or edge type.

In a closed graph,

Each node has one or multiple labels, each edge has one label.
Nodes or edges of the same type have the same set of properties.

While the graph type can be altered after a graph is created, its defined data model ensures consistent structure, guaranteeing high data integrity and consistency.

Node/Edge Type

Syntax

Syntax
<node type> ::=
  "NODE" [ "TYPE" ] <node type name> "(" [ <additional labels> ] [ <property types> ] ")"

<edge type> ::=
  "EDGE" [ "TYPE" ] <edge type name> <source node type reference> 
  "-[" [ <additional labels> ] [ <property types> ] "]->" <destination node type reference>

<additional labels> ::=
  < ":" | "IS" > <label name> [ { "&", <label name> } ... ]

<property types> ::=
  "{" <property type> [ { "," <property type> } ... ] "}"

<property type> ::=
  <property name> <property value type>

Each node or edge type has a unique type name, and is associated with a set of labels and property types. Each property type is defined with a property name and a property value type.

Labels

The node or edge type name automatically becomes a label. The label set of a node or edge type is the union of its type name and additional labels (optional).

When no additional labels are specified, the type name is the only label:

GQL
-- label set: [User]
NODE User ({name STRING})

Add additional labels:

GQL
-- label set: [User, Employee]
NODE User (:Employee {name STRING})

GQL
-- label set: [User, Employee, Manager]
NODE User (:Employee&Manager {name STRING})

Edge Type Endpoints

Edge types can specify source and destination node types, where <source/destination node type reference> is () or (<labels>). The <labels> is matched against the label sets of node types.

GQL
-- The FOLLOWS edge connects any two nodes
EDGE FOLLOWS ()-[{createdOn LOCAL DATETIME}]->()

-- The JOINS edge connects source nodes whose label set is [User,Employee] to destination nodes whose label set is [Company]                  
EDGE JOINS (:User&Employee)-[{title STRING}]->(:Company)

Creating Closed Graphs

Inline Graph Type

Create a closed graph g2 with inline graph type specification, which defines:

Node type User with properties name (STRING type) and age (UINT32 type)
Node type Club with a property name (STRING type)
Edge type FOLLOWS with a property createdOn (LOCAL DATETIME type)
Edge type JOINS with no properties

GQL
CREATE GRAPH g2 {
  NODE User ({name STRING, age UINT32}),
  NODE Club ({name STRING}),
  EDGE FOLLOWS ()-[{createdOn TIMESTAMP}]->(),
  EDGE JOINS ()-[]->()
}

Defined Graph Type

Create a closed graph g3 based on the defined graph type named gType (How to manage graph types), you have three equivalent GQL options to specify the graph type to be used:

GQL
CREATE GRAPH g3 gType

or

GQL
CREATE GRAPH g3 :: gType

or

GQL
CREATE GRAPH g3 TYPED gType

The graph g3 is created with all the types and properties defined within the graph type gType.

Managing Graph Types

The graph type defines structural rules for graphs by outlining the allowed node and edge types. You can define and store graph types in the database, making them reusable when creating new graphs.

Showing Graph Types

Show graph types defined in the database:

GQL
SHOW GRAPH TYPES

Each graph type provides the following essential metadata:

Field	Description
`name`	The unique name assigned to the graph type.
`node_type_count`	Number of node types.
`edge_type_count`	Number of edge types.
`node_types`	Comma-separated list of node type names.
`edge_types`	Comma-separated list of edge type names.
`definition`	The type definitions.
`bound_graphs`	Graphs that use this graph type.
`comment`	The comment of the graph type.
`created_at`	Creation time.
`updated_at`	Last update time.

Creating Graph Types

Create a graph type gType:

GQL
CREATE GRAPH TYPE gType {
  NODE User ({name STRING, age UINT32}),
  NODE Club ({name STRING}),
  EDGE FOLLOWS ()-[{createdOn TIMESTAMP}]->(),
  EDGE JOINS ()-[]->()
}

Dropping Graph Types

Drop the graph type gType:

GQL
DROP GRAPH TYPE gType

The IF EXISTS clause is used to prevent errors when attempting to delete a graph type that does not exist. It allows the statement to be safely executed.

GQL
DROP GRAPH TYPE IF EXISTS gType

This deletes the graph type gType only if a graph type with that name does exist. If gType does not exist, the statement is ignored without throwing an error.

Showing Node/Edge Types

Show node types defined in the current graph:

GQL
SHOW NODE TYPES

Show edge types defined in the current graph:

GQL
SHOW EDGE TYPES

Each type provides the following metadata:

Field	Description
`type`	`NODE` or `EDGE`.
`name`	The name of the type.
`properties`	The associated property definitions.

Showing Labels

Show labels in the current graph:

GQL
SHOW LABELS

Show node labels in the current graph:

GQL
SHOW NODE LABELS

Show edge labels in the current graph:

GQL
SHOW EDGE LABELS

Each label provides the following essential metadata:

Field	Description
`label`	The name of the label.
`type`	The type of the label, `NODE` or `EDGE`.

Altering Graph Types

You can alter the graph type of an existing closed graph.

Adding Node/Edge Types

Add a node type Book in the graph g2:

GQL
ALTER GRAPH g2 ADD NODE Book ({name STRING, author STRING})

Add an edge type PURCHASED in the graph g2:

GQL
ALTER GRAPH g2 ADD EDGE PURCHASED (:User)-[{createdOn TIMESTAMP}]->(:Book)

Adding Properties

Add a property gender to the node type User in the current graph:

GQL
ALTER NODE User ADD PROPERTY gender STRING

Add a property memberNo to the edge type JOINS within the current graph:

GQL
ALTER EDGE JOINS ADD PROPERTY memberNo INT32

Renaming Node/Edge Types

To rename the node type User to People in the current graph:

GQL
ALTER NODE User RENAME TO People

To rename the edge type FOLLOWS to LINKS in the current graph:

GQL
ALTER EDGE FOLLOWS RENAME TO LINKS

Renaming Properties

To rename the property name to title for the node type Book in the current graph:

GQL
ALTER NODE Book PROPERTY name RENAME TO title

To rename the property memberNo to memberNumber for the edge type JOINS in the current graph:

GQL
ALTER EDGE JOINS PROPERTY memberNo RENAME TO memberNumber

Dropping Node/Edge Types

A node or edge type can only be dropped when no nodes or edges of that type exist.

Drop the node type User from the graph g2:

GQL
ALTER GRAPH g2 DROP NODE User

Drop the edge type FOLLOWS from the graph g2:

GQL
ALTER GRAPH g2 DROP EDGE FOLLOWS

Dropping Properties

When a property is dropped, all related data - including the property values, associated indexes, and cached values - is permanently removed.

Drop the property name from the node type User in the current graph:

GQL
ALTER NODE User DROP PROPERTY name

Drop the property createdOn from the edge type FOLLOWS in the current graph:

GQL
ALTER EDGE FOLLOWS DROP PROPERTY createdOn