IHE XDS leans heavily on SOAP for its transactions. To retrieve the meta data from the IHE XDS environment it uses an ITI-18 transaction.
The IHE XDS Registry webservice can be accessed to download the WSDL. But you will need to provide us a certificate in order to be able to connect to the environment.
Alternatively you can find the WSDL files within the Open eHealth Integration Platform, see https://github.com/oehf/ipf/tree/master/commons/ihe/xds/src/main/resources/wsdl for the WSDL per transaction.