eXrQuy: Order Indifference in XQuery

There are more spots than immediately obvious in XQuery expressions where order is immaterial for evaluation-this affects most notably, but not exclusively, expressions in the scope of unordered { } and the argument of fn:unordered( ). Clearly, performance gains are lurking behind such expression contexts but the prevalent impact of order on the XQuery semantics reaches deep into any compliant XQuery processor, making it non-trivial to set this potential free. Here, we describe how the relational XQuery compiler Pathfinder uniformly exploits such order indifference in a purely algebraic fashion: Pathfinder-emitted plans faithfully implement the required XQuery order semantics but (locally) ignore order wherever this is admitted.

• Type: Conference
• Year: 2007
• Where: ICDE
• Authors: Torsten Grust, Jan Rittinger, Jens Teubner
• Keywords: Compliant Xquery Processor, Database, ICDE 2007, Xquery Compiler Pathfinder, XQuery Order Semantics