Flow policies: specification and enforcement

This paper deals with the problem of secure cooperative updates for XML documents in distributed systems. In particular, we introduce the basic notions underlying a flow language by using which a user can specify the flow that a given XML document has to follow within a group of cooperating subjects. A key feature of the flow language is to be based on the notion of subject credentials. In addition, we describe a policy language to specify special-purpose authorizations allowing selected subjects to modify or extend a given document flow. Finally, we briefly describe the protocols for verifying that the path followed by a document in a collaborative group agrees with the specified flow and to verify that modifications on a given flow are in accordance with the specified authorizations.