Relational Web Services

XQuery on the Web talks about Xquery: Meet the Web.

Dare quotes: "In fact, this separation of the private and more general query mechanism from the public facing constrained operations is the essence of the movement we made years ago to 3 tier architectures. SQL didn't allow us to constrain the queries (subset of the data model, subset of the data, authorization) so we had to create another tier to do this.

What would it take to bring the generic functionality of the first tier (database) into the 2nd tier, let's call this "WebXQuery" for now. Or will XQuery be hidden behind Web and WSDL endpoints?"

And responds with:
"Every way I try to interpret this it seems like a step back to me. It seems like in general the software industry decided that exposing your database & query language directly to client applications was the wrong way to build software and 2-tier client-server architectures giving way to N-tier architectures was an indication of this trend."

"Data model subsets" - don't you mean views?

Also Dare says, "All this indirection with WSDL files and SOAP headers yet functionality such as what Yahoo has done with their Yahoo! News Search RSS feeds isn't straightforward. I agree that WSDL annotations would do the trick but then you have to deal with the fact that WSDL's themselves are not discoverable."

Which I would refer anyone interested to the paper in the JOWS: Automated Discovery, Interaction and Composition of Semantic Web Services.

XML For You and Me, Your Mama and Your Cousin Too "At this point if you are like me you might suspect that defining that the web service endpoints return the results of performing canned queries which can then be post processed by the client may be more practical then expecting to be able to ship arbitrary SQL/XML, XQuery or XPath queries to web service end points.

The main problem with what I've described is that it takes a lot of effort. Coming up with standardized schema(s) and distributed computing architecture for a particular industry then driving adoption is hard even when there's lots of cooperation let alone in highly competitive markets."