In: Bericht Nr. 165, Fachbereich Informatik, Universität Hamburg. 1994.
Abstract: The notion of linear place invariants for coloured nets is extended to include sums of non-linear functions. The extension applies for such places where all tokens are removed by the occurrence of an output transition. The result serves to understand the relation of place invariants of coloured nets in comparison with traditional Floyd invariants of programs. In the second part, the property of token clearing is introduced to the occurrence rule, showing that the results of the first part are still valid. Such types of nets are important for the modelling of systems e.g. with respect to fault tolerant applications using recovery mechanisms. The last section recalls the notion of selfmodifying S/T-nets and offers a new formal definition. The invariant theorem is reformulated for this subclass and examples are studied.