A Survey of Petri Nets Slicing <s> Wangyang Slicing <s> Petri nets provide a means for modelling and verifying the behavior of concurrent systems. Program slicing is a well-known technique in imperative programming for extracting those statements of a program that may affect a given program point. In the context of Petri nets, computing a net slice can be seen as a graph reachability problem. In this paper, we propose two slicing techniques for Petri nets that can be useful to reduce the size of the considered net, thereby simplifying subsequent analysis and debugging tasks by standard Petri net techniques. <s> BIB001 </s> A Survey of Petri Nets Slicing <s> Wangyang Slicing <s> Petri net models are frequently complex and difficult to understand and modify. Slicing technology is very useful in analyzing programs, and has been widely used in specification level for model reduction. So it is necessary to explore slicing methods for Petri nets. This paper proposes a dynamic slicing technique for Petri nets based on the structural dependency graph (SDG). Firstly, the SDG is constructed from the slicing criterion by a backtracking algorithm. Secondly, based on the SDG and a given marking, the dynamic slice can be acquired. As a case study, the proposed method is applied to a control system, and a simulation tool is developed for validating this method and automatically generating the slice. The algorithms can be useful in automatically identifying the parts of the model that affect a state of interest, and provide the basic technical support for alleviating the difficulty of formal verification and analysis. <s> BIB002
Wangyang et al. presented another slicing algorithm to improve testing  . Later on, they proposed some improvements in Ref. BIB002 . The basic idea of the proposed algorithm in Ref.  is similar to the algorithm proposed by Lloren et al. BIB001 . At first, for both algorithms, a backward slice (see Algorithm 7) is computed for a given criterion place(s). Secondly, in the case of Llorens et al., a forward slice is computed for the complete Petri net model; whereas in the case of Wangyang et al., a forward slice is computed for the resultant Petri net model obtained from static backward slice. Let's suppose that there are n number of places in a Petri net model. Now, after applying the backward slicing algorithm, let's assume that there are n/2 number of places. The algorithm of Llorens et al. will compute the forward slice for n number of places, whereas the Wangyang et al. algorithm will compute the forward slice only for n/2. The algorithm starts by taking a backward sliced Petri net model and producing a local reachability graph LRG for the Petri net model. LRG is a directed graph, where its node set is the set of places and the mark of an arc is a transition. From the initially marked places, a root node is constructed and then the enabled transitions are added together with their places. If the old node can contribute tokens to new ones, then the LRG (PN ) can be obtained by tracking the backward static slice forward and the parts associated with slicing criterion under the initial marking m 0 . Finally, the backward slice can be obtained being coupled with the initial marking and corresponding flow relation. Consider the example of the Petri net model shown in Figure 19 , where its resultant sliced net for the criterion place B consists of transition t1 and its incoming place.