SOAP / XML / ORACLE

Good day to you all.

Up until now I have been designing & developing apps in Oracle using PL/SQL and the web toolkit for this. This at the moment is on 8i (8.1.6+) and still using OWAS 3.0 in development.

A prospective project would involve exchanging data with a 3rd party system. The API definitions doc for this system talks of SOAP, Web Services Definition Language and XML.

I gather that the idea is that "SystemA" can request something be done in "SystemB" when these two systems can be built in entirely different technologies but communicating via a standard protocol.

I need a primer in understanding where these 'new' (to me!) technologies sit as well as, if possible, simple examples of the technology put into practise - perhaps there is a good website you know of?

The other thing I need is to know whether it is essential for me to upgrade to 9iAS in order to use these newer technologies (perhaps also Oracle 9i too?). I'm assuming the answer to this is probably a resounding "Yes!" but thought I'd ask anyway.

Thanks for any & all pointers!

TIA

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Jeremy Ovenden