Comments on “Liveness of an extended ” [Automatica 46 (2010) 1008–1018]

In a recent paper (Liu et al., 2010), a new deadlock prevention method was proposed based on the concepts of generalized circular waits and circular blockings for WS 3 PR (an extension to System of Simple Sequential Processes with Resources ( S 3 PR ) with weighted arcs). It is proved that a WS 3 PR net model with a certain characteristic structure is live with respect to a class of initial markings. However, some results developed in Liu et al. (2010) are not correct, which are discussed in this correspondence paper.