1. A system for carrying out jobs on documents, comprising: transformation units that in cooperation generate a target document from a source document for carrying out a job, wherein a document is stored according to a document model as a structure of component, a component has a component state assigned, and a document has a document state assigned, the document state comprising component states, the transformation units having the abiltiy to bring a component from a first state into a second state; means for composing a digraph of transformation units that is able to transform components of a document in such a way that the document is brought from a source document state to a target document state; and means for managing processing of components by the transformation units according to the digraph of transformation units.