A Compact In-Memory Dictionary for RDF data

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Abstract

While almost all dictionary compression techniques focus on static RDF data, we present a compact in-memory RDF dictionary for dynamic and streaming data. To do so, we analysed the structure of terms in real-world datasets and observed a high degree of common prefixes. We studied the applicability of Trie data structures on RDF data to reduce the memory occupied by common prefixes and discovered that all existing Trie implementations lead to either poor performance, or an excessive memory wastage. In our approach, we address the existing limitations of Tries for RDF data, and propose a new variant of Trie which contains some optimizations explicitly designed to improve the performance on RDF data. Furthermore, we show how we use this Trie as an in-memory dictionary by using as numerical ID a memory address instead of an integer counter. This design removes the need for an additional decoding data structure, and further reduces the occupied memory. An empirical analysis on realworld datasets shows that with a reasonable overhead our technique uses 50–59% less memory than a conventional uncompressed dictionary.
Original languageEnglish
Title of host publicationThe Semantic Web: Latest Advances and New Domains - 12th European Semantic Web Conference, ESWC 2015, Proceedings
PublisherSpringer/Verlag
Pages205-220
Number of pages16
Volume9088
ISBN (Electronic)9783319188171
DOIs
Publication statusPublished - 2015
Event12th European Semantic Web Conference (ESWC 2015) - Portoroz, Slovenia
Duration: 31 May 20154 Jun 2015

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume9088
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference12th European Semantic Web Conference (ESWC 2015)
CountrySlovenia
CityPortoroz
Period31/05/154/06/15

Bibliographical note

Proceedings title: Proceedings of the twelfth European Semantic Web Conference
Publisher: Springer
Place of publication: Berlin

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