is it possible to call a Web Service from within an XQuery expression like you can do with User defined Table Functions in SQL?
The only thing i found for this is an extension for XQuery1.0 called a Web Services Facility. Is there a more standardized way to call web services?
You can make HTTP Requests from XQuery in eXist using the EXPath http-client library that @dirkk pointed out to you. With regards to SOAP, there is no special support for this in eXist, but that is only because you don't need anything special. SOAP messages are just XML documents and so you can construct your messages in XQuery like any other document, likewise you can process the SOAP response as it is just an XML document that comes back from the call to the http-client.