corner: a completeness reasoner for sparql queries over rdf data sources
DESCRIPTION
With the increased availability of data on the Semantic Web, the question whether data sources offer data of appropriate quality for a given purpose becomes an issue. With CORNER, we specifically address the data quality aspect of completeness. We demonstrate a formal way to state for which topics an RDF source is complete and how to use such statements to automatically analyze whether a given query will return a complete answer over a source. CORNER supports SPARQL BGP queries and can take RDFS ontologies into account in its analysis. If a query can only be answered completely by a combination of sources, CORNER rewrites the original query into one with SPARQL SERVICE calls, which assigns each query part to a suitable source, and executes it over those sources. CORNER builds upon previous work by Darari et al. and is implemented using standard Semantic Web frameworks.TRANSCRIPT
CORNER:A Completeness Reasoner for the Semantic Web1
Fariz Darari
Radityo Eko PrasojoWerner Nutt
EPCL Workshop 2014, Dresden
1to be demonstrated at ESWC 2014Fariz Darari (EPCL Workshop 2014) CORNER 1 / 14
Introduction
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Introduction
Completeness statement about the IMDB data source
Quentin Tarantinowas the character
Mr. Brown
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http://www.imdb.com/title/tt0105236/fullcredits?ref_=tt_ov_st_sm#cast
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Introduction
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Introduction
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Motivations
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Motivations
Darari et al.2 developed a logical framework forcompleteness reasoning techniques on the SWThe framework enables creation of descriptions as to whichparts of a data source are complete, called completenessstatementsChecks whether a query returns a complete result, calledquery completeness checks, are then possible
2Fariz Darari, Werner Nutt, Giuseppe Pirró, Simon Razniewski:Completeness Statements about RDF Data Sources and Their Use for QueryAnswering. ISWC 2013Fariz Darari (EPCL Workshop 2014) CORNER 7 / 14
Motivations
However, implementation is still missingWe built an implementation of the framework, calledCORNER
A Web-based demo can be accessed athttp://corner.inf.unibz.it/
Implementation reused the Apache Jena (Semantic Weblibrary) and Google Web Toolkit (User Interface library)
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System Architecture
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System Architecture
Completeness reasoning steps:From the query Q, CORNER generates an initial graph Gi
Qrepresenting the information needed for answering thequeryEvery completeness statement C is translated into aSPARQL CONSTRUCT query QC
Application of all the queries QC to the graph GiQ results in a
subgraph GaQ of Gi
Q, representing parts of the query forwhich data are completeBy evaluating Q over Ga
Q, CORNER tests whether thecomplete data are sufficient to answer Q
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Demo
DEMO
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Bonus: CANDy
CANDy = Completeness-Aware Querying and Navigationon the Web of DataGoals:
To develop techniques to leverage meta-information aboutthe completeness of data sources for navigation andqueryingTo reconcile the two paradigms of open- and closed-worldsemantics underlying RDF and SPARQL, respectively
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CANDy: Techniques for completenessreasoning
Research in progress:Queries and completeness statements with comparisonsQuantitative completeness reasoningCompleteness reasoning in the domain of streamprocessingCompleteness statements mining from the Web
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CANDy: Reconciling the open- and closedworld semantics
Research in progress:Correctness and completeness of non-monotonic queriesUNA vs non-UNA paradigms on completeness reasoning
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