Sorry, I probably wasn't clear in my initial question. What I meant is how do DAG based workflows deal with computational graphs that contains cycles? Eg. we ha

Sorry, I probably wasn't clear in my initial question. What I meant is how do DAG based workflows deal with computational graphs that contains cycles? Eg. we have 2 states: Cart and Payment and 2 events: PutItem and Checkout. A simple (external) DSL describing this graph could look like: Cart --PutItem--> Cart Cart --Checkout-> Payment Does the workflow engine in the article exclude situations like this? Regarding forking what I meant is that if you have: A --event--> B ^ / \--undo---/ then if your invariant is to be a DAG then you could "unroll" the cycle into some new state C that you would make semantically equivalent to A. A --event--> B --undo--> C This works but causes state explosion.