from the ref manual:

"The Master is just an implementation of a Spring Batch Step, with the ItemWriter replaced with a generic version that knows how to send chunks of items to the middleware as messages. The Slaves are standard listeners for whatever middleware is being used (e.g. with JMS they would be MesssageListeners), and their role is to process the chunks of items using a standard ItemWriter or ItemProcessor plus ItemWriter, through the ChunkProcessor interface."

might be easier to discuss in a few.