Pushdown Compression

The pressing need for eficient compression schemes for XML documents has recently been focused on stack computation [6, 9], and in particular calls for a formulation of information-lossless stack or pushdown compressors that allows a formal analysis of their performance and a more ambitious use of the stack in XML compression, where so far it is mainly connected to parsing mechanisms. In this paper we introduce the model of pushdown compressor, based on pushdown transducers that compute a single injective function while keeping the widest generality regarding stack computation. The celebrated Lempel-Ziv algorithm LZ78 [10] was introduced as a general purpose compression algorithm that outperforms finite-state compressors on all sequences. We compare the performance of the Lempel-Ziv algorithm with that of the pushdown compressors, or compression algorithms that can be implemented with a pushdown transducer. This comparison is made without any a priori assumption on the data's source and considering the asymptotic compression ratio for infinite sequences. We prove that Lempel-Ziv is incomparable with pushdown compressors

Middleware für Ubiquitäre Systeme: Ein Modellgetriebener Ansatz

Dieser Dissertation liegt die Hypothese zugrunde, dass modell-getriebene Softwareentwicklung (MDSD) den Widerspruch zwischen "top-down"- und "bottom-up"- Entwicklung durch einen "middle-out" Ansatz auflöst, welcher zwischen Technologie und Abstraktion vermittelt. MDSD wird als Mittel verwendet, um Middleware für Ubiquitäre Systeme auf dem einen Turm von Modellen zu bauen, ohne den Bezug zur konkreten Technologie zu verlieren

Pushdown compression

24 pagesInternational audienceThe pressing need for efficient compression schemes for XML documents has recently been focused on stack computation (Hariharan and Shankar 2006, League and Eng 2007), and in particular calls for a formulation of information-lossless stack or pushdown compressors that allows a formal analysis of their performance and a more ambitious use of the stack in XML compression, where so far it is mainly connected to parsing mechanisms. In this paper we introduce the model of pushdown compressor, based on pushdown transducers that compute a single injective function while keeping the widest generality regarding stack computation. The celebrated Lempel-Ziv algorithm LZ78 was introduced as a general purpose compression algorithm that outperforms finite-state compressors on all sequences. We compare the performance of the Lempel-Ziv algorithm with that of the pushdown compressors, or compression algorithms that can be implemented with a pushdown transducer. This comparison is made without any a priori assumption on the data's source and considering the asymptotic compression ratio for infinite sequences. We prove that Lempel-Ziv is incomparable with pushdown compressors

Polylog space compression is incomparable with Lempel-Ziv and pushdown compression

This paper considers online compression algorithms that use at most polylogarithmic space (plogon). These algorithms correspond to compressors in the data stream model. We study the performance attained by these algorithms and show they are incomparable with both pushdown compressors and the Lempel-Ziv compression algorithm