ECST – Extended Context-Free Straight-Line Tree Grammars

• Published in: Data Science pp. 186 - 198
• Main Authors: Böttcher, Stefan, Hartel, Rita, Jacobs, Thomas, Jeromin, Markus
• Format: Book Chapter
• Language: English
• Published: Cham Springer International Publishing
• Series: Lecture Notes in Computer Science
• Subjects: Grammar-based compression; Updating compressed XML data
• ISBN: 9783319204239; 3319204238
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-319-20424-6_18

Grammar-based compressors like e.g. CluX [1], BPLEX [2], TreeRePAIR [3] transform an XML tree X into a context-free straight-line linear tree (CSLT) grammar G and yield strong compression ratios compared to other classes of XML-specific compressors. However, CSLT grammars have the disadvantage that simulating on G update operations like inserting, deleting, or re-labeling a node V of X requires to isolate the path from X’s root to V from all the paths represented by G. Usually, this leads to an increased redundancy within G, as grammar rules are copied and modified, but the original and the modified grammar rules often differ only slightly. In this paper, we propose extended context-free straight-line tree (ECST) grammars that allow reducing the redundancy created by path isolation. Furthermore, we show how to query and how to update ECST compressed grammars.