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Petri nets are a graphical and mathematical tool used for modelling and studying concurrent, parallel, distributed and discrete event systems (Murata, 1989). Till date they have been successfully applied to various knowledge-based systems like biological networks, communication networks, industrial systems etc. due to their ability to represent any graph-based systems (Murata, 1989; Chaouiya, 2007; Marwan, Wagler & Weismantel, 2011; Reddy, Mavrovouniotis, & Liebman, 1993).
Various approaches have been applied to model the biological networks and Petri nets have been proved to be a promising and effective tool for the modelling and analysis of biological networks. In 1962, a German mathematician Carl Adam Petri first introduced the concept of Petri nets in his Doctoral Dissertation 'Communication with Automata' as a graphical and mathematical tool (Petri, 1966). Several theories from the authors from different backgrounds in different timeframe are available in the literature. For example, most recent proposed theory for 1-safe petri net is Boolean petri net (Kansal, Acharya & Singh, 2012; Kansal, Singh & Acharya, 2010, 2011, 2015; Singh, Kansal & Acharya, 2013). Apart from theory part, modelling and study of biological networks using PNs have been and are continuing to be a growing interest among the researchers due to the power of Petri nets to model complex situations. Various extensions of Petri nets such as hybrid PNs, stochastic PNs, colored PNs and hybrid functional PNs have also been used to model different types of biological networks (Chaouiya, 2007; Hardy & Robillard, 2004).
The metabolic networks play an important part in an organism’s life since its life is dependent on its metabolism. The metabolic pathways can be regarded as subsystems of a metabolic network. A metabolic pathway is an interlinked network of biochemical reactions, catalyzed by enzymes. In these series of reactions, the output of a reaction can become the reactant for next reaction. To intuitively understand the behavior of such complex reactions, both qualitative and quantitative modelling of metabolic pathways is much needed.