edd dumbill serves up a great overview of the role played by xml in the next-generation web, with a superb discussion on rdf and soap:

“In sum, SOAP provides a web-aware alternative to current object protocols like CORBA. It has a low cost of deployment and is supported by software right now. It still has issues to face in terms of interoperability, security, and description/discovery infrastructure.

RDF implements a computer-readable alternative to current web knowledge representation applications (i.e., HTML). It faces some immediate challenges in terms of intelligibility and immediate business uses are less than certain. In the long run, though, it presents the opportunity to transform the way the web is used.

Looking at the big picture, one can envisage SOAP and RDF operating in a complementary manner in the Web of the future. RDF-based technology can provide directory information to describe and locate SOAP services. SOAP could carry RDF graphs in between RDF aggregation services, or provide a “virtual graph” service from a provider like Amazon.com.

Both SOAP and RDF have a part to play in my dream of a totally integrated future. However, they also point to the need for some very significant work, only just getting started, on agreeing upon XML vocabularies and semantics. That is a hard problem, one which I expect will never be totally solved, and may cause us to develop the best “nearly-there” solutions we can, to continue getting the most out of the Web.”

edd’s last comment is, of course, the ‘devil’s in the details’ type of thing – but at least a few bright people are working towards the semantic web [ and here ]. you’re in big trouble if you miss what the semantic web isn’t:

“There are many other data models which RDF’s Directed Labelled Graph (DLG) model compares closely with, and maps onto. This page is written with the intention of enumerating the similarity and diferences between the models, to indicate how the mapping might be done and what extra information muast be added in the process. Where the other models are related to previous unmet promises of computer science, now passed into folk law as unsolvable problems, they suggest a fear that the goal of a Semantic Web is inappropriate.

One consistent difference between the Semantic Web and many data models for programming langauges is the “closed world assumption”.”

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