Lecture Notes in Computer Science, 1999, Volume 1660/1999, 69-81, DOI: 10.1007/3-540-48057-9_6

Implementing Reversed Alternating Finite Automaton (r-AFA) Operations

Sandra Huerter, Kai Salomaa, Xiuming Wu and Sheng Yu

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Abstract

In [17], we introduced a bit-wise representation of r-AFA, which greatly improved the space efficiency in representing regular languages. We also described our algorithms and implementation methods for the union, intersection, and complementation of r-AFA. However, our direct algorithms for the star, concatenation, and reversal operations of r- AFA would cause an exponential expansion in the size of resulting r-AFA for even the average cases. In this paper, we will design new algorithms for the star, concatenation, and reversal operations of r-AFA based on the bit-wise representation introduced in [17]. Experiments show that the new algorithms can significantly reduce the state size of the resulting r- AFA. We also show how we have improved the DFA-to-AFA transformation algorithm which was described in [17]. The average run time of this transformation using the modified algorithm has improved significantly (by 97 percent).
This research is supported by the Natural Sciences and Engineering Research Council of Canada grants OGP0041630.

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