The synchronisation of n≥ 2 heterogenously typed models requires a thorough understanding of global consistency rules. After having related these models by determining identical entities in them, we express the global rules in terms of diagrammatic predicates imposed on a comprehensive metamodel, which integrates the structural properties of all involved model spaces. If the global rules are violated, a possible subsequent consistency restoration can make use of formal descriptions for the verification of these rules. The comprehensive metamodel is constructed in the category of directed graphs. If there is an arbitrary number of related models, comprehensive artefacts can formally be represented by colimits, i.e. by universal categorical constructions. The goal of the paper is to establish a practical algorithm for this construction. The main example, a web service integration scenario from the health care domain, also shows that relating graph morphisms may be non-injective, which is incorporated into the algorithm.