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copied!<p>Study the <a href="http://docs.jboss.org/jbpm/v3/userguide/jpdl.html" rel="nofollow noreferrer">Java Process Definition Language specification</a> where <a href="http://www.jboss.org/jbpm" rel="nofollow noreferrer">JBoss has an execution engine for it</a>. Using this Java based engine may be your easiest solution, and it solves many of the problems you've outlined. </p> <p>If you intend to write your own, you will probably end up modelling states and transitions, vertices and edges in a directed graph. And this as Ciaran Archer wrote are the components of a <a href="http://en.wikipedia.org/wiki/Finite-state_machine" rel="nofollow noreferrer">State Machine</a>. The best persistence approach IMO is capturing versions of whatever data is being sent through workflow via serialization, capturing the current state, and a history of transitions between states and changes to that data. The mechanism probably needs a way to keep track of who or what has responsibility for taking the next action against that workflow. </p> <p>Based on your question, one thing to consider is whether or not you really need to represent parallel tasks in your solution. Where instead it might be possible to en-queue a set of messages and then specify a wait state for all of those to complete. Representing actual parallelism implies you are moving <em>data</em> simultaneously through several different processes. In which case when they join again you need an algorithm to resolve deltas, which is very much a non trivial task. </p> <p>In the context of ColdFusion and what you're trying to accomplish, a scheduled task may be necessary if the system you're writing needs to poll other systems. Consider WDDX as a serialization format. JSON, while seductively simple, I recall has some edge cases around numbers and dates that can cause you grief. </p> <p><a href="https://stackoverflow.com/questions/4801987/suggest-a-persistent-strategy-for-a-workflow-system/4819408#4819408">Finally see my answer to this question for some additional thoughts</a>.</p>

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