R-Programs: A Framework for Distributing XML Structural Joins across Function Calls
Structural joins and, in particular, twig joins are essential operations in XML query processing. Algorithms presented so far treat a twig join as a single operator with multiple inputs. However, in XQuery and XSLT, a twig pattern may be scattered across several functions (templates); thus, function integration is required before the application of a twig join operator. This paper presents R-programs – a novel evaluation framework based on an expanding network of operators. In this environment, a function may repeatedly and bidirectionally interact with its caller; consequently, a structural join algorithm may be distributed across the boundary of a function. Given this ability, function integration is no longer required and twig join algorithms become applicable even in the presence of recursive functions.
KeywordsFunction Call Path Solution Call Tree XPath Expression Call Operation
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