Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/data-types/graph-element-reference-type/
Documentation version: v5.3.2

# Graph element reference types

Graph element reference types represent references to nodes or edges in a graph:

- `NODE`: Node reference value type.
- `EDGE`: Edge reference value type.

A reference value identifies a graph element; it is not a copy of the graph element's properties. You can access the properties of the referenced node or edge through the reference value. `NODE` and `EDGE` cannot be used as node or edge property types.

## Get graph element reference values

Variables in graph element patterns hold references to the matched graph elements. For example:

````
'''
USE movie
MATCH (a@Actor)-[e@Act]->(m@Movie)
RETURN a, e, a.name
LIMIT 1
'''

````

In this query:

- `a` and `m` hold node reference values.
- `e` holds an edge reference value.
- `a.name` accesses the `name` property of the referenced node.

## View graph element reference types

The `typeof()` function returns the complete type of a reference value:

````
'''
USE movie
MATCH (a@Actor)-[e]->(m@Movie)
RETURN typeof(a) AS node_type, typeof(e) AS edge_type
LIMIT 1
'''

````

Return:

````
+---------------+------------------------------+
| node_type     | edge_type                    |
+---------------+------------------------------+
| Node<(Actor)> | Edge<(Actor)-[Act]->(Movie)> |
+---------------+------------------------------+

````

`NODE` and `EDGE` are generic reference value types. `Node<(Actor)>` includes the referenced node type. `Edge<(Actor)-[Act]->(Movie)>` includes the referenced edge type and its source and destination node types.

## Difference from graph element types

Reference value types are different from the node and edge types defined in a graph type.

 | Term | Example | Meaning
 | Node reference value type | `NODE`, `Node<(Actor)>` | Value type of a query variable or parameter
 | Node type | `NODE TYPE Actor` | A category of nodes defined in a graph type
 | Edge reference value type | `EDGE`, `Edge<(Actor)-[Act]->(Movie)>` | Value type of a query variable or parameter
 | Edge type | `EDGE TYPE Act` | A category of edges defined in a graph type

## Use as procedure parameter types

When you define a user-defined procedure (UDP), you can declare an input parameter as `NODE` or `EDGE`:

````
parameter_name NODE
parameter_name EDGE

````

A `NODE` parameter accepts a node reference value, and an `EDGE` parameter accepts an edge reference value. For the complete syntax, see [CREATE PROCEDURE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/procedures/create/#parameter_type).

## Limitations

- `NODE` and `EDGE` cannot be used as node or edge property types.
- Reference equality means that two references identify the same graph element, not that two distinct graph elements happen to have identical property values.