1. A method executed at least in part in a computing device for providing a workflow with a dynamic reference activity, the method comprising: receiving a workflow definition that includes at least one reference activity; when the reference activity is reached at runtime, determining a referred activity associated with the referenced activity; providing an error message associated with the referred activity in response to an inability to retrieve the referred activity while validating the referred activity; retrieving and initializing the referred activity; executing the referred activity at least partially based on an argument and a property of the reference activity; returning a result of the referred activity execution to the reference activity; and forwarding the result from the reference activity to a subsequent activity in the workflow.