How to capture the location of a WSDL document for a service entity

In the Technical Note Using WSDL in a UDDI Registry, Version 2.0.2,
Section 2.3.4 General Conventions it is said that:
"The location of the WSDL document that defines the WSDL entity is
captured for portType, binding and, optionally, service entities."

It is clear that the location of the WSDL document is modeled in the
overviewURL for portType and binding entities (that are mapped into
tModel) but how to capture this information for service entities?