Transformationas of Derivation Sequences in Graph Grammars

Basing on the Church-Rosser Theorems in /EK 76b/ analysis and synthesis of parallel derivations in graph grammars are introduced. This allows specific, transparent transformations of derivation sequences, which can be used as elementary steps of algorithms acting on derivations, and the calculation rules for transformations presented in this paper are needed to prove the correctness of such algorithms. One example of this kind is given: the equivalence of derivations in graph grammars is defined and canonical derivations representing the equivalence classes are specified. For graph grammars canonical derivations will be as important as leftmost derivations and respective concepts for classical Chomsky grammars to the design of correct parsing algorithms.