Straight-line programs (SLPs) offer powerful text compression by representing a text T [1, u] in terms of a restricted context-free grammar of n rules, so that T can be recovered in O(u) time. However, the problem of operating the grammar in compressed form has not been studied much. We present a grammar representation whose size is of the same order of that of a plain SLP representation, and c...

We study several extensions of the notion of alternation from context-free grammars to context-sensitive and arbitrary phrase-structure grammars. Thereby new grammatical characterizations are obtained for the class of languages that are accepted by alternating pushdown automata.

We give efficient ranking and unranking algorithms for left Szilard languages of context-free grammars. If O(n2) time and space preprocessing is allowed then each ranking operation is possible in linear time. Unranking takes time O(n log n). These algorithms imply similar algorithms for context-free languages generated by arbitrary unambiguous context-free grammars.

XML is successful as a machine processable data interchange format, but it is often too verbose for human use. For this reason, many XML languages permit an alternative more legible non-XML syntax. XSLT stylesheets are often used to convert from the XML syntax to the alternative syntax; however, such transformations are not reversible since no general tool exists to automatically parse the alte...

One of the main unresolved problems in data mining is related with the treatment of data that is inherently sequential. Algorithms for the inference of association rules that manipulate sequential data have been proposed and used to some extent but are ineffective, in some cases, because too many candidate rules are extracted and filtering the relevant ones is difficult and inefficient. In this...

In modern mathematics, graphs figure as one of the better-investigated class of mathematical objects. Various properties of graphs, as well as graph-processing algorithms, can be useful if graphs of a certain kind are used as denotations for CF-grammars. Furthermore, graph are well adapted to various extensions (one kind of such extensions being attributes). This paper describes a class of grap...

We introduce the problem of grammar mining, where patterns are context-free grammars, as a generalization of a large number of common pattern mining tasks, such as tree, sequence and itemset mining. The proposed system offers data miners the possibility to specify and explore pattern domains declaratively, in a way which is very similar to the declarative specification of regular expressions in...

Several recent works have studied subfamilies of deterministic context-free languages with good closure properties, for instance the families of input-driven or visibly pushdown languages, ormore generally families of languages accepted by pushdown automatawhose stack height can be uniquely determined by the input word read so far. These ideas can be described as a notion of synchronization. In...

Grammar-based compression algorithms infer context-free grammars to represent the input data. The grammar is then transformed into a symbol stream and finally encoded in binary. We explore the utility of grammar-based compression of DNA sequences. We strive to optimize the three stages of grammar-based compression to work optimally for DNA. DNA is notoriously hard to compress, and ultimately, o...