18. A non-transitory machine-readable storage medium according to claim 17 , the method further comprising: providing the decision tree for detecting the predetermined data, the decision tree comprising a plurality of states, each of said plurality of states being linked with at least one other state by a respective condition, an arrangement of linked states forming a plurality of paths in the tree; comparing the token types of the sequence of tokens to respective conditions in the decision tree to match the sequence of tokens to one or more paths in the tree; and detecting the predetermined data without using an epsilon reduction to take account of said at least one optional token type.
18. A non-transitory machine-readable storage medium according to claim 17 , the method further comprising: providing the decision tree for detecting the predetermined data, the decision tree comprising a plurality of states, each of said plurality of states being linked with at least one other state by a respective condition, an arrangement of linked states forming a plurality of paths in the tree; comparing the token types of the sequence of tokens to respective conditions in the decision tree to match the sequence of tokens to one or more paths in the tree; and detecting the predetermined data without using an epsilon reduction to take account of said at least one optional token type. 19. A non-transitory machine-readable storage medium according to claim 18 , the method further comprising: providing a path in the decision tree for the predetermined data including a token of the at least one optional token type; and providing a separate path for the predetermined data without the token of the at least one optional token type.