That's correct.
About your questions you can also use JMS persistent and replicated queues to handle such situations.
Aboutmy book, that would be a recommended lecture if you have a developerprofile. I'm currently writing a new version of the book targeted tojBPM5 that includes a lot of new concepts and features.
You canalso start reading about integration patterns to understand some of thecommon practices used in the industry to coordinate systeminteractions, but once again that's pretty technical and not high level(business analyst level) readings.
Cheers!