..........................................NEXT PREVIOUS INDEX
L04 FSA: Non-deterministic FSA - Intro FSA: Non-determinism o So far, transition matrix is a function, i.e., a unique state in any transition from any state. Called deterministic FSA (DFSM or DFSA or DFA). o A FSM in which more than one transition possible from any one of the states is called non-deterministic FSM (NFSM or NFSA). + Ex.: An NDFA for dates in Feb. one ... twenty ------>------ / \ Feb / \ ->(q0)-->--(q1)-->--(q2)-->--((q3)) twenty one ... nine - Note: From state q1, two possible transitions on input of 'twenty' (to q2 or q3). Therefore, NFSA. - Why have NFSA? Ans: Easier to build NFSA for some problems. Humans do case analysis, but the cases may not be disjoint. Leads to non-determinism. o Meaning: If it is possible to reach an accepting state (through some path) for an input, accept the input. one ---------->--------- | ... | | twenty | 0 | ------>-----\ | ---->---- | / \ | / \ Feb |/ \|/ 2001 \ ->(q0)-->--(q1)-->--(q2)-->--((q3))-->---- (q4) \ twenty | one | ^ \ | ... | / \ |-->---| / \ nine / \ / \-------->---------/ 2001 o Empty transition: Also leads to NFSA - Empty transition is an arc labelled with the empty string (i.e., 0) * Meaning: Without consuming any input, the machine can follow the transition arc. + Ex.: %% To put an example %%..........................................NEXT PREVIOUS INDEX