what is glushkov NFA. What is the difference between Glushkov NFA and Thompson NFA? I saw this term "Glushkov NFA" at http://lambda-the-ultimate.org/node/2064 . Search engines are returning references to articles that use glushkov nfa, but nothing specific about the glushkov nfa itself. 

What is Glushkov NFA? How different is it from the NFA created from Thompson Construction?
The most significant difference is that Glushkov's NFA does not use $\epsilon$-transitions.  Very roughly, the algorithm indexes the characters in the regular expression from left to right.  Each state in the NFA is a subset of possible indices of the last character read from the input string.

Glushkov's construction [3] is described in detail in Aho, Sethi, and Ullman's classical compiler textbook, aka "The Dragon Book" [1].  The same construction was also described earlier by McNaughton and Yamada [4] and later  by Berry and Sethi [2], so you may find it easier to search under those names.


A. V. Aho, R. Sethi, and J. D. Ullman.  Compilers: Principles, Techniques, and Tools. Addison-Wesley, 1988.
G. Berry and R. Sethi. From regular expressions to deterministic automata.  Theoretical Computer Science 48:117–126, 1986.
V. M. Glushov.  The abstract theory of automata.  Russian Mathematical Surveys 16:1–53, 1961.
R. McNaughton and H. Yamada.  Regular expressions and state graphs for automata.  IEEE Trans. Electronic Computers 9(1):39–47, 1960.