Suppose that I create three taskInstance of one task, taskInstance1, taskInstance2, taskInstance3. TaskInstance1 put a variable xxx=1 into its contextInstance. TaskInstance2 get xxx=1 from the contextInstance, and just before taskInstance2 wants do something depends on the value of xxx, taskInstance3 update xxx to 3.

How does JBPM promise the correctness of sharing limited resources?

Same doubt about variable "unfinishedTask".