Transformations of Graph Grammars

The notion of multilevel graph representations, where parts of graphs are not visible and the information can be restored via the explicit application of productions, and the corresponding extension of the classical double pushout approach is generalized to the algebraic theory of graph grammars and to the rewriting of these grammars, at the global level by defining High Level Replacement Systems where the productions consist of grammars and grammar morphisms, and at the local level where standard productions are used to rewrite both the initial graph and the productions of a grammar.