Merging Hierarchically-Structured Documents in Workflow Systems

We consider the manipulation of hierarchically-structured documents within a complex workflow system. Such a system may consist of several subsystems distributed over a computer network. These subsystems can concurrently update partial views of the document. At some points in time we need to reconcile the various local updates by merging the partial views into a coherent global document. For that purpose, we represent the potentially-infinite set of documents compatible with a given partial view as a coinductive data structure. This set is a regular set of trees that can be obtained as the image of the partial view of the document by the canonical morphism (anamorphism) associated with a coalgebra (some kind of tree automaton). Merging partial views then amounts to computing the intersection of the corresponding regular sets of trees which can be obtained using a synchronization operation on coalgebras.