Schema-based Scheduling of Event Processors and Buffer Minimization for Queries on Structured Data Streams

Abstract

We introduce an extension of the XQuery language, FluX, that supports event-based query processing and the conscious handling of main memory buffers. Purely event-based queries of this language can be executed on streaming XML data in a very direct way. We then develop an algorithm that allows to efficiently rewrite XQueries into the event-based FluX language. This algorithm uses order constraints from a DTD to schedule event handlers and to thus minimize the amount of buffering required for evaluating a query. We discuss the various technical aspects of query optimization and query evaluation within our framework. This is complemented with an experimental evaluation of our approach. * Work support by project Z29-N04 of the Austrian Science Fund (FWF).

Streamable Fragments of Forward XPath

“…Similar kinds of tree automata were proposed for processing Xml streams already in [20,18,17]. Note that these tree automata provide an explicit "visual" stack in contrast to standard tree automata.…”

“…The objective of this paper is to narrow this gap by providing new positive and negative results for fragments of Forward XPath. Our approach relies on the relationship between temporal logics for unranked trees [16], which abstracts from the concrete syntax of XPath, and tree automata for Xml streams [1,20,18].…”

Efficient Streaming Algorithms for Tree Matching Problems

“…The method proposed in [40] is a general strategy, but requires exponential time (O(|T|⋅2 |Q| )) in the worst case, as analyzed in [40]. The methods discussed in [32,33] [12]. The algorithm discussed in [23] greatly improves TwigM, running in O(|Q|⋅|T|) time and O(|Q|⋅r) caching space.…”

“…One is for the so-called XML streaming environment and the other is index-based. A great many strategies have been proposed to evaluate XPath queries in an XML streaming environment [2,12,18,23,27,32,33,39,40] . The methods discussed in [2,27] are based on finite state automata (FSA), but only able to handle single path queries, i.e., a query containing branching cannot be processed, as observed in [39].…”

Ordered Types for Stream Processing of Tree-Structured Data

“…(An exception is Frisch and Nakano's work 9) , which will be addressed later.) In those approaches, the source languages for describing tree-processing programs are more restricted than ordinary programming languages (query language 4) , and attribute grammars 5)-8) ). On the other hand, the source language in our framework is an ordinary functional programming language.…”