Hermann K.-G. Walter

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Promise problems have been introduced in 1985 by S.Even e.a. as a generalization of decision problems. Using a very general approach we study solvability and unsolvability conditions for promise problems of set families and languages. We show, that cores of un-solvability are completely determined by partitions of cohesive sets. We prove the existence of(More)
Biomass waste, including municipal solid waste (MSW), contains lignocellulosic-containing fiber components that are not readily available as substrates for anaerobic digestion due to the physical shielding of cellulose imparted by the nondigestible lignin. Consequently, a substantial portion of the potentially available carbon is not converted to methane(More)
We show that grammar forms, introduced by S. Ginsburg, can be treated with the help of grammar homomorphisms, introduced by G. Hotz. This gives us the possibility to generalize the notion of grammar forms in such a way that we can prove closure properties of the associated language family using some simple axioms by diagram chasing. Moreover we demonstrate(More)