Fast Answering of XPath Query Workloads on Web Collections

2008 IEEE 24th International Conference on Data Engineering

Khatchadourian

et al. 2008

Self Cite

Abstract-DescribeX is a visual, interactive tool for exploring the underlying structure of an XML collection. DescribeX implements a framework for creating XML summaries described using axis path regular expressions (abbreviated AxPRE). AxPRE's capture all the bisimilarity-based proposals in the summary literature and they can be used to define new and more expressive summaries. This demonstration shows how DescribeX helps to analyze diverse XML collections in one particular scenario: the analysis of protein-protein interaction XML data from multiple providers that conform to the PSI-MI schema. I. OVERVIEWXML has been adopted as the standard format for numerous applications in data exchange, web-based feeds (blogs, news feeds, podcasts), hypertext collections, and web services. XML schemas are used across different application domains for validating domain-specific XML instances. Schema validation provides a strong basis from which to structure, author and interpret XML data. However, even though two XML collections can be validated against a common schema, the actual structure of the XML instances may be quite different in each of the two collections. This situation may occur because the common schema is extended to allow different user communities to combine schemas freely (e.g., RSS extensions like Yahoo! Media), or document designers may restrict themselves to use just a subset of a larger schema (e.g., best practice guidelines of industry standards like those for IXRetail 1 ). In these scenarios, schemas do not provide sufficient information for understanding the structural commonalities of a given collection.DescribeX is a visual, interactive tool for exploring the underlying structure of an XML collection, capable of handling gigabyte-size datasets. DescribeX is based on a framework (presented in [1] and [2]) for creating XML summaries based on axis path regular expressions (AxPRE, for short). DescribeX summaries are specified by a partition created using the novel notion of bisimilarity applied to subgraphs described by an AxPRE. The elements in the extent of a given partition (represented by a node in the summary) can be computed by an XPath query that is constructed by DescribeX. By employing different AxPREs to define the summary partition, DescribeX can capture all the bisimilarity-based proposals in the existing literature, plus it can also define new and more expressive summaries.The graph based visualization employed by DescribeX makes it straightforward to see the different path structures 1 http://www.nrf-arts.org/ that are present in the collection. The application of local node refinements (ie, changing an AxPRE at a given summary node to a different, more detailed AxPRE) can reveal detailed substructure variations. DescribeX functionality helps a user in quickly understanding what parts of the schema are used in practice. Further analysis to find the most common structures and substructures can then be performed in DescribeX through the application of coverage. This provides a strong indicati...

Section: Overviewmentioning

confidence: 99%

DescribeX: Interacting with AxPRE Summaries

Ali

2008 IEEE 24th International Conference on Data Engineering

Khatchadourian

et al. 2008

Self Cite

“…One type of summary which does this by grouping common substructures is a structural summary. Prior work has shown the usability of XML path summaries for a variety of scenarios within semi-structured XML collections such as XPath query answering [9] and information retrieval [3]. Recently, structural summaries have been proposed in the context of RDF data in [21], but for frequency estimation applied to query evaluation (also the most common use for summaries in the context of XML), but not for describing usage in a flexible manner as done in this work.…”

Section: Introductionmentioning

confidence: 97%

ExpLOD: Summary-Based Exploration of Interlinking and RDF Usage in the Linked Open Data Cloud

Khatchadourian

Lecture Notes in Computer Science

2010

Self Cite

Abstract. Publishing interlinked RDF datasets as links between data items identified using dereferenceable URIs on the web brings forward a number of issues. A key challenge is to understand the data, the schema, and the interlinks that are actually used both within and across linked datasets. Understanding actual RDF usage is critical in the increasingly common situations where terms from different vocabularies are mixed. In this paper we describe a tool, ExpLOD, that supports exploring summaries of RDF usage and interlinking among datasets from the Linked Open Data cloud. ExpLOD's summaries are based on a novel mechanism that combines text labels and bisimulation contractions. The labels assigned to RDF graphs are hierarchical, enabling summarization at different granularities. The bisimulation contractions are applied to subgraphs defined via queries, providing for summarization of arbitrary large or small graph neighbourhoods. Also, ExpLOD can generate SPARQL queries from a summary. Experimental results, using several collections from the Linked Open Data cloud, compare the two summary creation approaches implemented by ExpLOD (graph-based vs. SPARQL-based).

“…This section provides an overview of the DescribeX framework (introduced in [3]). The framework includes a powerful language based on axis path regular expressions (AxPREs) for describing the extents in an SD.…”

Section: Axpre Summariesmentioning

confidence: 99%

“…Since then, research on summaries has focused mostly on query evaluation, indexing and selectivity estimation. Although these are all interesting problems we can address (see [3] for XPath query evaluation using DescribeX), in this paper we focus on metadata exploration, which has become increasingly relevant over the last few years and has received considerably less attention in the summary literature. AxPRE summaries have a unique capability that makes them suitable for describing the (semi-)structure of XML collections: they are the first summaries capable of describing and refining partitions created using a powerful language.…”

Section: Introductionmentioning

confidence: 99%

AxPRE Summaries: Exploring the (Semi-)Structure of XML Web Collections

2008 IEEE 24th International Conference on Data Engineering

Rizzolo

Vaisman

2008

Self Cite

Abstract-This paper introduces AxPRE summaries, a formalism that allows exploring the (semi-)structure of large XML collections. AxPRE summaries are implemented in a tool, DescribeX, that supports visualizing XML collections via summaries that can be interactively refined using a powerful and descriptive axis path regular expression language. Experimental results on gigabyte collections have shown that this flexibility does not come at the expense of efficiency.