Contextual grammars and natural languages
Handbook of formal languages, vol. 2
Automata for matching patterns
Handbook of formal languages, vol. 2
Efficient string matching: an aid to bibliographic search
Communications of the ACM
Marcus Contextual Grammars
Text Compression Using Antidictionaries
ICAL '99 Proceedings of the 26th International Colloquium on Automata, Languages and Programming
Pattern Matching in Text Compressed by Using Antidictionaries
CPM '99 Proceedings of the 10th Annual Symposium on Combinatorial Pattern Matching
On the Complexity of Finite Sequences
IEEE Transactions on Information Theory
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We consider the data compression using antidictionaries and give algorithms for faster compression and decompression. While the original method of Crochemore et al. uses finite transducers with ε-moves, we (de)compress using ε-free transducers. This is provably faster, assuming data non-negligibly compressible, but we have to consider the overhead due to building the new ma-chines. In general, they can be quadratic in size compared to the ones allowing ε-moves; we prove this bound optimal as it is reached for de Bruijn words. However, in practice, the size of the ε-free machines turns out to be close to the size of the ones allowing ε-moves and therefore we can achieve significantly faster (de)compression. We show our results for the files in Calgary corpus.