The BPEL service engine requires strict usage of correlation sets. Currently the validation system does not detect violations of the following requirements:
On Message: The On Message element must have a valid <correlations> child if the On Message is used in a Pick activity that does not have the createInstance="yes" attribute.
Receive: The Receive element must have a valid <correlations> child if it does not have the createInstance="yes" attribute.
On Event: The On Event element must have a valid <correlations> child.
See the NetBeans IDE 6.1 Release Notes for other known issues for the SOA pack.