I would like to know if it's possible to retrieve all the tasks defined inside a jbpm process. I know I can retrieve the one that is ready to execute (filtering by actor or group), but is there a way to get all the tasks defined in this process as soon as the process instance has started?
Not unless the process has reached its last node. But if you are only looking for information at node level and not at task level then you can get all the nodes of the process immediately after its start.
Node information would be the name of the node, coordinates etc.