Evaluating Complex Queries Against XML Streams with Polynomial Combined Complexity

Olteanu, Dan; Furche, Tim; Bry, François

doi:10.1007/978-3-540-27811-5_4

Cited by 14 publications

(11 citation statements)

References 7 publications

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“…A query is compiled into a DAG structure where nodes are XPath nodetests and edges are XPath axes. The reverse axes are rewritten similar to [16] using rewrite rules of [15]. The evaluation is based on the incremental construction of a matching structure consisting of mappings of nodes from the DAG query to nodes from the tree conveyed in the input stream.…”

Section: Related Workmentioning

confidence: 99%

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SPEX: Streamed and Progressive Evaluation of XPath

Olteanu

2007

IEEE Trans. Knowl. Data Eng.

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Abstract-Streams are preferable over data stored in memory in contexts where data is too large or volatile, or a standard approach to data processing based on storing is too time or space consuming. Emerging applications such as publishsubscribe systems, data monitoring in sensor networks, financial and traffic monitoring, and routing of MPEG-7 call for querying streams. In many such applications, XML streams are arguably more appropriate than flat streams, for they convey (possibly unbounded) unranked ordered trees with labeled nodes. However, the flexibility enabled by XML streams in data modeling makes query evaluation different from traditional settings and challenging.This article describes SPEX, a streamed and progressive evaluation of XPath. SPEX compiles queries into networks of simple and independent transducers and processes XML streams with polynomial combined complexity. This makes SPEX especially suitable for implementation on devices with low-memory and simple logic as used, e.g., in mobile computing.

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Section: Related Workmentioning

confidence: 99%

“…Chronologically, SPEX is the first streamed Core XPath processor to enjoy polynomially combined complexity [16]. This contrasts with most approaches to streamed evaluation, which have exponential query complexity, e.g., [8]- [11].…”

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confidence: 99%

SPEX: Streamed and Progressive Evaluation of XPath

Olteanu

2007

IEEE Trans. Knowl. Data Eng.

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“…SPEX (streaming) [32,31] tree tree The essential observation from twig joins is that, we need to limit the space (and management overhead) for describe the relations between potential matches of different variables. In twig joins, the combination of tree data and tree queries with only child and descendant relations together with an efficient stack management ensures this property.…”

Section: Foundation: Tree Labelingmentioning

confidence: 99%

Labeling RDF Graphs for Linear Time and Space Querying

Furche

Weinzierl

Bry

2009

Semantic Web Information Management

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Abstract. Indices and data structures for web querying have mostly considered tree shaped data, reflecting the view of XML documents as tree-shaped. However, for RDF (and when querying ID/IDREF constraints in XML) data is indisputably graph-shaped. In this chapter, we first study existing indexing and labeling schemes for RDF and graph data in general with focus on support for efficient adjacency and reachability queries. For XML, labeling schemes are an important part of the widespread adoption of XML, in particular for mapping XML to existing (relational) database technology. However, the existing indexing and labeling schemes for RDF (and graph data in general) sacrifice one of the most attractive properties of XML labeling schemes, the constant time (and per-node space) test for adjacency (child) and reachability (descendant). In the second part, we introduce the first labeling scheme for RDF data that retains this property and thus achieves linear time and space processing of acyclic RDF queries on a significantly larger class of graphs than previous approaches (which are mostly limited to tree-shaped data). Finally, we show how this labeling scheme can be applied to (acyclic) SPARQL queries to obtain an evaluation algorithm with time and space complexity linear in the number of resources in the queried RDF graph.

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“…PDA-based: Where twig joins assume one stream of nodes from the input document for each stack (and thus XPath step), the third class of approaches based on pushdown automata aims to evaluate XPath queries on a single input stream similar to a SAX event stream. SPEX, e.g., [118,119,117] also maintains a record of partial answers for each XPath step, but minimizes used memory more efficiently and exploits the existential nature of most XPath steps by maintaining only generic conditions rather than actual pointers to elements from the XML stream (except for candidates of the actual results set, of course). Also it supports all XPath axes in contrast to the twig join approaches.…”

Section: Comparisonmentioning

confidence: 99%

Four Lessons in Versatility or How Query Languages Adapt to the Web

Bry¹,

Furche²,

Linse³

et al. 2009

Semantic Techniques for the Web

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Abstract. Exposing not only human-centered information, but machine-processable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule-and pattern based query language that aims to give shield application builders from much of this complexity: In a single query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C's GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for querying XML and RDF in the same way. (3) We show that the resulting query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space querying also for many RDF graphs. We believe that Web query languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a "Web of Data".

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Evaluating Complex Queries Against XML Streams with Polynomial Combined Complexity

Cited by 14 publications

References 7 publications

SPEX: Streamed and Progressive Evaluation of XPath

SPEX: Streamed and Progressive Evaluation of XPath

Labeling RDF Graphs for Linear Time and Space Querying

Four Lessons in Versatility or How Query Languages Adapt to the Web

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