eXist An Open Source Native XML Database.pdf

eXist: An Open Source Native XML Database Wolfgang Meier Darmstadt University of Technology meier@ifs.tu-darmstadt.de Abstract. With the advent of native and XML enabled database systems, tech- niques for efficiently storing, indexing and querying large collections of XML documents have become an important research topic. This paper presents the storage, indexing and query processing architecture of eXist, an Open Source native XML database system. eXist is tightly integrated with existing tools and covers most of the native XML database features. An enhanced indexing scheme at the architecture’s core supports quick identification of structural node relationships. Based on this scheme, we extend the application of path join al- gorithms to implement most parts of the XPath query language specification and add support for keyword search on element and attribute contents. 1. Overview eXist () is an Open Source effort to develop a native XML database system, which can be easily integrated into applications dealing with XML in a vari- ety of possible scenarios, ranging from web-based applications to documentation systems running from CDROM. The database is completely written in Java and may be deployed in a number of ways, either running as a stand-alone server process, inside a servlet-engine or directly embedded into an application. eXist provides schema-less storage of XML documents in hierarchical collections. Using an extended XPath syntax [2, 6], users may query a distinct part of the collec- tion hierarchy or even all the documents contained in the database. Despite being lightweight, eXist’s query engine implements efficient, index-based query processing. An enhanced indexing scheme supports quick identification of structural relationships between nodes, such as parent-child, ancestor-descendant or previous-/next-sibling. Based on path join algorithms, a wide range of path expression queries is processed only using index information. Acce