Deferred Node-copying Scheme for XQuery Processors

XQuery is generic, widely adopted language for querying and manipulating XML data. Many of currently available native XML databases are using XQuery as its primary query language. The XQuery specification requires each XML node to belong to exactly one XML tree. In case of the XML subtree is appended into a new XML structure, the whole subtree has to be copied. This may lead into excessive and unnecessary data copying and duplication. In this paper, we present a new XML node copying scheme that defers the node data copy operation unless necessary. We will show that this schemes significantly reduces the XML node copy operations required during the query processing.