1. A computer implemented method for generating a bit map for a deterministic finite automata based graph, the method comprising: given a current node and an arc pointing from the current node to a next node, analyzing valid arcs in the graph to determine which of the valid arcs are valid arcs pointing from the next node; constructing a bit map associated with the arc pointing from the current node to the next node, the bit map representing the valid arcs pointing from the next node; and storing the bit map representing the valid arcs pointing from the next node in the arc pointing from the current node to the next node to enable the bit map to be evaluated and the valid arcs pointing from the next node to be identified from the evaluation of the bit map without the next node being read.