Abstract. We consider global dynamics of reaction systems as introduced by Ehrenfeucht and Rozenberg. The dynamics is represented by a directed graph, the so-called transition graph, and two reaction systems are considered equivalent if their corresponding transition graphs are isomorphic. We introduce the notion of a skeleton (a one-out graph) that uniquely defines a directed graph. We provide the necessary and sufficient conditions for two skeletons to define isomorphic graphs. This provides a necessary and sufficient condition for two reactions systems to be equivalent, as well as a characterization of the directed graphs that correspond to the global dynamics of reaction systems.

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openAccessArticle: FalsePage Range: 108-108doi: 10.1016/j.tcs.2011.12.029Harvest Date: 2016-01-12 15:08:57issueName: Magic in Sciencecover date: 2012-04-20pubType

Reaction systems, introduced by Ehrenfeucht and Rozenberg, are a theoretical model of computation based on the two main features of biochemical reactions: facilitation and inhibition, which are captured by the individual reactions of the system. All reactions, acting together, determine the global behavior or the result function, res, of the system. In this paper, we study decomposing of a given result function to find a functionally equivalent set of reactions. We propose several approaches, based on identifying reaction systems with Boolean functions, Boolean formulas, and logic circuits. We show how to minimize the number of reactions and their resources for each single output individually, as a group, and when only a subset of the states are considered. These approaches work both when the reactions of the given res function are known and not known. We characterize the minimal number of reactions through the minimal number of logical terms of the Boolean formula representation of the reaction system. Finally, we make applications recommendations for our findings.

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For a family of sets we consider elements that belong to the same sets within the family as companions. The global dynamics of a reactions system (as introduced by Ehrenfeucht and Rozenberg) can be represented by a directed graph, called a transition graph, which is uniquely determined by a one-out subgraph, called the 0-context graph. We consider the companion classes of the outsets of a transition graph and introduce a directed multigraph, called an essential motion, whose vertices are such companion classes. We show that all one-out graphs obtained from an essential motion represent 0-context graphs of reactions systems with isomorphic transition graphs. All such 0-context graphs are obtained from one another by swapping the outgoing edges of companion vertices.