WSDL definitions / targetNamespace

Can anyone help me understand the use of the (optional) targetNamespace on the WSDL 1.1 defintions tag?

The value can clearly be different from any targetNamespace(s) on schema elements in the types section., but is often the same in simple examples.

One use for the targetNamespace at the defintions level seems to be to restrict imports of other WSDL files (they must all have the same targetNamespace). Other issues which occur to me are:

- if I'm using rpc style then the outer level tag of a SOAP request is derived from the WSDL operation name (i.e. it isn't defined in Schema). Do these outer tags in the SOAP instance document belong to the namespace defined at the WSDL defintions level? (With their child elements potentially belonging to other namespaces as specified on WSDL schema elements?)

- if there is no targetNamespace attribute on a WSDL schema element, does it default to the target namespace of the defintions element?

- if there is no targetNamespace on the WSDL defintions element?

Many thanks!
Rob