A workflow is a long-duration multi-step activity. In this paper we are interested in workflows that execute under the control of various processing stations that may be located at different nodes of a distributed system. The stations may be autonomous and only partially automated. We present the design and a proposed implementation of a new model for workflow management that is based on a concept of an Information Carriers (INCA). Workflow computations are carried out as interactions between INCAs and the processing stations with the locus of control of a computation migrating with the workflow. The model presented is modular in the sense that modification of a sub-activities of the workflow does not necessarily require changes to the workflow specification. Furthermore, the model preserves the autonomy of the processing stations and does not require them to change the means they use to process the individual steps of the workflow activity.