A BPEL program simulator can include a document object modeler configured to arrange activities defined by a BPEL document into a document object model (DOM) tree. The DOM tree can include activity nodes and links between the activity nodes. The BPEL program simulator further can include simulation logic configured to process the activity nodes to emulate at least one BPEL activity selected from the group consisting of Sequence, Flow, While, Pick and OnMessage, Switch and Case, Invoke, Script, Receive, Reply, Empty, Staff, and Assign.