1. A computer-assisted method for automatically assigning work tasks to users in a workflow management system, comprising the steps of providing at least one first directed graph and at least one second directed graph that respectively comprise objects and connections between these objects, wherein objects, the connections of which originate directly or indirectly from a parent object, form sub objects of this object, providing at least two different authorization categories, wherein a first authorization category represents a local authorization that is limited to the respective object and a second authorization category represents an authorization that applies to the respective object and at least part of the sub-objects of this object, assigning, with respect to a user, an authorization category to at least one object in the first graph and to at least one object in the second graph in order to respectively obtain at least one assigned object, forming the Cartesian product of the first and the second graph in order to obtain a product graph, identifying the product object of the product graph resulting from the assigned object of the first graph and the assigned object of the second graph and identifying sub-objects of the product object, to which the second authorization category also applies, if applicable, assigning the user to the identified product object and the identified sub-objects of the product graph, obtaining a responsibility request with respect to a requested object of the product graph, determining the user assigned to the requested object, and assigning the request to the user.