This paper describes the implementation of a workflow management system to support mobile GIS workgroup applications and highlights the design of the workflow definition language the system offers. The system features a hierarchical execution model in which each instance is able to delegate the execution of sub-workflows to other active instances. It incorporates instance discovery and event handling services, that enhance the proper treatment of disconnections, and adopts an optimist replication strategy to handle workflow context variables. The workflow definition language features special constructors that improve the legibility of large workflow definitions. The results reported here build on the experience accumulated with the implementation and deployment of an emergency management application that offers action plans, easy access to geographic data and tight control over the resources allocated to face an emergency.