Handles and reachability analysis of free choice nets

In this paper, we discuss on the reachability analysis of free choice nets based on structure theory associated to handles. First half of the paper is devoted to clarify the relationship between handles and deadlocks/traps from the aspect emphasized on the reachability analysis, In the second half of the paper, the reachability criteria for free choice nets is discussed based on the structure theory. The reachability rendition is expressed in terms of token distribution at the initial or end marking in an appropriately reduced net associated token-free deadlocks or traps. On reachability points of view, classes of Petri nets discussed in the paper involve several important classes of Petri nets as its special cases. The result is extended to extended free choice nets.