Formal description of NFA operation

Question

What do you mean by Formal description of NFA operation ?

Answer 1

NFA  M = (Q, Σ, δ, q₀, F)

accepts a string w = w₁ w₂ w₃ … w_n ∈ Σ*

if w can be written (by inserting ε’s) as:

y = y₁ y₂ y₃ … y_m ∈ (Σ ∪ {ε})*
and ∃ sequence r₀ ,r₁,…,r_m of states for which

– r₀ = q₀

– r_i+1 ∈ δ(r_i, y_i+1) for i = 0, 1, 2, .... m-1

- r_m ∈ F