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Of course to turn this on it's head, (the XML As Complex System and the XML=WAP threads are converging), we should step back as posters have hinted and ask, if XML is not self-describing (really, what does an XML instance say about its application semantics), how should we be doing that? Some current candidates: 1. Laissez-faire: send only the message. You have an agreement or trust the other guy's process. You might augment this with a checking service, say one that goes out and compares prices to ensure the other guy is giving you the best deal (time-sensitive). 2. Schema/DTD travels with message. That is the SGML Way. It works if you want ultimate one-connect shopping. It seems to be a big part of some implementations. Best applied, IMO, to infrequent but noise-critical communications. You send the test because you absolutely want the receiver to understand this message. 3. Ask the Web: use RDF or some other expert system what is needed. Isn't this sort of a dictionary? It works as long as you own or accept the ontology of others. This is Trust and Verify. Advantages? 4. Send the code. Java folks like that. This is the ultimate, Trust Me, I Own The Process approach. Augmented with a way to export the information on request, it is easy for end users despite any problems of performance, proprietary languages, etc. Others? If we say that meaning is discoverable, we play right into the web services paradigm as I understand it. Get only as much semantic as we recognize easily, negotiate the rest, then document the negotiation results and hold the communication process to those results. That this is still in the main, contract-based document processing shouldn't disenchant or disappoint. Humans have worked like this for a very long time very successfully and all this paradigm does is amplify that and take out some noise. Given that organizations are competent at creating their own definitions, the requirement for standard schemata isn't critical, although it saves a lot of work and things go quickly. That is pretty much all any SGML project from CALS or even the old GenCode and GML projects promised anyway. len
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