# Identifier

External unique object identifier published by the responsible body, which may be used by external applications to reference the spatial object.

{% hint style="info" %}
External object identifiers are distinct from thematic object identifiers.
{% endhint %}

{% hint style="info" %}
The voidable version identifier attribute is not part of the unique identifier of a spatial object and may be used to distinguish two versions of the same spatial object.
{% endhint %}

{% hint style="info" %}
The unique identifier will not change during the lifetime of a spatial object.
{% endhint %}

## Identifier attributes

### localId

A local identifier, assigned by the data provider. The local identifier is unique within the namespace, that is, no other spatial object carries the same unique identifier.

* Note: It is the responsibility of the data provider to guarantee uniqueness of the local identifier within the namespace.
* **Type:** CharacterString 
* **Multiplicity:** \[1]

### namespace

Namespace uniquely identifying the data source of the spatial object.

{% hint style="info" %}
The namespace value will be owned by the data provider of the spatial object and will be registered in the INSPIRE External Object Identifier Namespaces Register.
{% endhint %}

* **Type:** CharacterString 
* **Multiplicity:** \[1]

### versionId

The identifier of the particular version of the spatial object, with a maximum length of 25 characters. If the specification of a spatial object type with an external object identifier includes lifecycle information, the version identifier is used to distinguish between the different versions of a spatial object. Within the set of all versions of a spatial object, the version identifier is unique.

{% hint style="info" %}
The maximum length has been selected to allow for time stamps based on ISO 8601, for example, “2007-02-12T12:12:12+05:30” as the version identifier.
{% endhint %}

{% hint style="info" %}
The property is void if the spatial data set does not distinguish between different versions of the spatial object; it is missing if the spatial object type does not support any lifecycle information.
{% endhint %}

* **Type:** CharacterString 
* **Multiplicity:** \[0…1]