Using XML to represent web service invocation.

[Paul Duffin]

As I understand it the WSIF is designed to allow Java code to
programmatically invoke any web service that has a wsdl description. The
client code does not have to know anything about specific bindings or
locations of web services, they just provide a url to the wsdl, the name
of the operation they want to invoke and any 'parameters'.

Assuming that the above is a correct (and probably simplistic) summary I
need to do a very similar thing except that I need to represent the web
service invocation using an abstract XML representation instead of
coding it directly into Java.

The WSDL contains an abstract XML representation of a message and so I
would like to use that if I could as it seems perfect for it. Section
2.3.2 of WSDL Note (http://www.w3.org/TR/wsdl#_abstract-v) even says

> Message definitions are always considered to be an abstract
> definition of the message content. A message binding describes how
> the abstract content is mapped into a concrete format. However, in
> some cases, the abstract definition may match the concrete
> representation very closely or exactly for one or more bindings, so
> those binding(s) will supply little or no mapping information.
> However, another binding of the same message definition may require
> extensive mapping information. For this reason, it is not until the
> binding is inspected that one can determine "how abstract" the
> message really is.

The first two sentences indicate to me that it should be possible to provide mappings direct from the abstract message format through to the underlying bindings. These mappings would only depend on the abstract message format and the binding type, they would not need application specific knowledge such as is required for mapping from Java objects through to specific bindings.

However, my problem is that I cannot seem to find any confirmation of my interpretation of the specification, either through examples of how it can be done, or code to actually do it.

I have read the WSDL many times now and the binding definitions do not seem to elaborate on ".. how the abstract content is mapped into a concrete format.". In particular it seems to be in need of a lot of examples that show how abstract message definitions (in XML Schema) are represented in each binding.

As WSIF operates at a similar abstract level I was wondering whether anyone on this group could enlighten me on whether it is possible and if so how, or even better tell me that WSIF already does this.

If it is not possible for all binding types / WSDL structures then I am prepared to limit its applicability, such as to the WS-I Basic Profile.

http://www.ws-i.org/Profiles/Basic/2003-01/BasicProfile-1.0-WGD.pdf