There is a new article available on developerWorks called Deploy Java UDRs through Web services on Informix using Rational Application Developer. It shows how to expose a Java UDR as a web service and serves as a useful introduction to Rational Application Developer.
Where it says to "install Informix Internet Foundation 2000" they mean "Informix Dynamic Server". (IIF 2000 was the IDS name around the time of version 9.21 if memory serves correctly, which it probably doesn't.)
Rational Application Developer and Java UDRs