#### 8.5.2.1 IfcURIReference

The IfcURIReference provides for identifying a Uniform Resource Identifier (URI). A URI can be classified as a locator or a name or both, that is it may comprise a Uniform Resource Locator (URL) and/or a Uniform Resource Name (URN).

- A Uniform Resource Locator, URL, is a string conforming to a standardized format, which refers to a resource on the internet (such as a document or an image) by its location.
- A Uniform Resource Name, URN, is intended to serve as persistent, location-independent resource identifier and is designed to make it easy to map other namespaces (that share the properties of URNs) into URN-space.

> NOTE See RFC 3986 for definition of Uniform Resource Identifier.

> HISTORY New defined datatype in IFC4.

XSD Specification:

<xs:simpleType name="IfcURIReference">
<xs:restriction base="xs:normalizedString"/>
</xs:simpleType>
<xs:element name="IfcURIReference-wrapper" nillable="true">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="ifc:IfcURIReference">
<xs:attributeGroup ref="ifc:instanceAttributes"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>

EXPRESS Specification:

TYPE IfcURIReference = STRING;
END_TYPE;

EXPRESS-G diagram

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