S2CX: From relational data via SQL/XML to (Un-)Compressed XML

• Published in: Information systems (Oxford) Vol. 56; pp. 198 - 213
• Main Authors: Böttcher, Stefan, Hartel, Rita, Wolters, Dennis
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2016
• Subjects: Compressed; Extensible Markup Language; Information systems; Queries; Query languages; Relational data bases; Representations; SQL/XML; XML; XML compression; XML generation from relational databases; SQL/XML; XML compression; XML generation from relational databases
• ISSN: 0306-4379; 1873-6076
• DOI: 10.1016/j.is.2015.09.011

The gap between storing data in relational databases and transferring data in form of XML has been closed e.g. by SQL/XML queries that generate XML data out of relational data sources. However, only few relational database systems support the evaluation of SQL/XML queries. And even in those systems supporting SQL/XML, the evaluation of such queries is quite slow compared to the evaluation of SQL queries. In this paper, we present S2CX, an approach that allows to efficiently evaluate SQL/XML queries on any relational database system, no matter whether it supports SQL/XML or not. As a result to an SQL/XML query, S2CX supports different output formats ranging from plain XML to different compressed XML representations including a succinct encoding of XML data, schema-aware compressed XML to grammar compressed XML. In many cases, S2CX produces compressed XML as a result to an SQL/XML query even faster than the evaluation of SQL/XML queries into non-compressed XML as provided by Oracle 11g and by DB2. Furthermore, our approach to query evaluation scales better, i.e., the larger the dataset, the faster is our approach compared to SQL/XML query evaluation in Oracle 11g and in DB2. •SQL/XML query evaluation generating compressed and non-compressed XML formats.•Supports SQL/XML on all relational databases, even those not supporting SQL/XML.•Generates directly compressed XML formats without need to generate XML format first.•In most cases, our approach outperforms SQL/XML query evaluation of DB2 and Oracle.•Our approach scales better than SQL/XML query evaluation of DB2 and of Oracle.