3 research outputs found
Parsing Unary Boolean Grammars Using Online Convolution
In contrast to context-free grammars, the extension of these
grammars by explicit conjunction, the so-called conjunctive
grammars can generate (quite complicated) non-regular languages
over a single-letter alphabet (DLT 2007). Given these
expressibility results, we study the parsability of Boolean grammars,
an extension of context-free grammars by conjunction and negation,
over a unary alphabet and show that they can be parsed in time O(|G| log^2(n) M(n))
where M(n) is the time to multiply two n-bit integers. This multiplication
algorithm is transformed into a convolution algorithm which in turn is
converted to an online convolution algorithm which is used for the parsing
Compressed Membership for NFA (DFA) with Compressed Labels is in NP (P)
In this paper, a compressed membership problem for finite automata, both
deterministic and non-deterministic, with compressed transition labels is
studied. The compression is represented by straight-line programs (SLPs), i.e.
context-free grammars generating exactly one string. A novel technique of
dealing with SLPs is introduced: the SLPs are recompressed, so that substrings
of the input text are encoded in SLPs labelling the transitions of the NFA
(DFA) in the same way, as in the SLP representing the input text. To this end,
the SLPs are locally decompressed and then recompressed in a uniform way.
Furthermore, such recompression induces only small changes in the automaton, in
particular, the size of the automaton remains polynomial.
Using this technique it is shown that the compressed membership for NFA with
compressed labels is in NP, thus confirming the conjecture of Plandowski and
Rytter and extending the partial result of Lohrey and Mathissen; as it is
already known, that this problem is NP-hard, we settle its exact computational
complexity. Moreover, the same technique applied to the compressed membership
for DFA with compressed labels yields that this problem is in P; for this
problem, only trivial upper-bound PSPACE was known