Modifying a componentized workflow model during execution of the workflow. Each step of the workflow is modeled as an activity that has metadata to describe design time aspects, compile time aspects, and runtime aspects of the workflow step. A user selects and arranges the activities to create the workflow via user interfaces or application programming interfaces. Metadata is associated with each of the activities in the workflow. During execution of the workflow, the user modifies the metadata to affect execution of the workflow without recompiling the workflow.