6. Entwicklung computergesttzter Informationssysteme

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W3C Technical Plenary Boston, 28 February 2005
Named Graphs meet SPARQL
Chris Bizer, Freie Universität Berlin,
GermanyJeremy Carroll, Hewlett-Packard Labs,
UK Pat Hayes, IHMC, USA Patrick Stickler, Nokia,
Finland
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SPARQL Version 20050217

• SELECT ?company ?rating
• WITH localtrustedInformation
  localcrawlerMonday localcrawlerTuesday
• FROM website1graph1 website1graph2
• website2graph1 website2graph2
• WHERE ( ?g dcpublisher ?name )
• ( ?name tpltrustedBy localMe )
• GRAPH ?g ( ?company finrating ?rating
  ) ( ?company finsector finbanking )

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RDF Dataset versus Named Graphs
Named Graphs
RDF Dataset
BackgroundGraph
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Agenda

• Implementing Named Graphs
• NG4J Named Graphs API for Jena
• Jena - Multimodel
• TriX and TriG Syntax
• Signing Named Graphs
• Semantic Web Publishing Vocabulary (SWP)
• Use Cases
• Versioning and Provenance

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NG4J Named Graphs API for Jena

• Extension to the Jena semantic web toolkit
• APIs for manipulating sets of Named Graphs
• Memory and database backed storage
• TriQL query language
• Serialization using TriX, TriG and collections of
  RDF/XML files
• SWP API for signing graphs
• Available under BSD license

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NG4Js APIs

• Named Graph API
• NamedGraph graph graphset.createGraph(graphname)
  
• graph.add(triple)
• Quad API
• graphset.addQuad(quad)
• Provenance enabled Jena Model API
• Model model graphset.asJenaModel("http//example
  .org/defaultgraph")
• iterator jenaStatement.listGraphNames()
• provides migration path for existing applications

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TriX

• Straight forward XML serialization of the
  abstract syntax
• allows the usage of generic XML tools like XSLT
  or XQuery

ltTriX xmlns"http//www.w3.org/2004/03/trix/trix-1
/"gt ltgraphgt lturigthttp//www.bizer.de/Informa
tionAboutRichardlt/urigt lttriplegt
lturigthttp//richard.cyganiak.de/foaf.rdfRichardCy
ganiaklt/urigt lturigthttp//xmlns.com/foaf/0.1/
mboxlt/urigt lturigtmailtorichard_at_cyganiak.delt/
urigt lt/triplegt lt/graphgt ltgraphgt
lturigthttp//www.bizer.de/ProvenanceInformationlt/ur
igt lttriplegt lturigthttp//www.bizer.de/Inf
ormationAboutRichardlt/urigt
lturigthttp//purl.org/dc/elements/1.1/authorlt/urigt
ltplainLiteralgtChris Bizerlt/plainLiteralgt
lt/triplegt lt/graphgtlt/TriXgt
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TriG

• based on Turtle, extended with graph naming

_at_prefix dc lthttp//purl.org/dc/elements/1.1/gt .
_at_prefix ex lthttp//www.example.org/vocabulary/gt
. _at_prefix lthttp//www.example.org/exampleDocume
nt/gt . G1 _Monica exname "Monica Murphy"
. _Monica exemail ltmailtomonica_at_murphy.or
ggt. G1 exdisallowedUsage exMarketing
G2 G1 exauthor Chris . G1 exdate
"2003-09-03"xsddate
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TriX, TriG and SPARQL Protocol getGraph()

• GET /qps?graph2.rdfgraph4.rdf HTTP/1.1Accept
  text/n3
• GetGraph returns the serialized RDFGraph
  identified by OperationTarget or all of the
  separately serialized RDFGraphs identifed by
  OperationTargetSet Protocol Spec
• Accept text/trig
• Avoids redundant transmission of namespace
  declarations
• Accept application/trix
• Allows the transformation of query results using
  XSLT

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SPARQL Protocol getGraph() and Wildcards

• Our experience Repositories quickly fill with
  hundreds of graphs.
• The query environment may provide the RDF
  dataset to be queried. SPARQL Query Language
  Spec
• Wildcards might also be useful in SPARQL
  Protocol.
• GET /qps?graph HTTP/1.1

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Publishing with Signatures

• Semantic Web Publishing Vocabulary (SWP-2)

• swpSignatureMethod specifies
• a graph canonicalization method
• a signature method provided by XML Signature

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Publishing with Signatures - Example

• G1 Monica exname "Monica Murphy .
  Chris exname "Chris Bizer" .
• G1 swpassertedBy G1 . G1
  swpauthority _s .
• G1 swpsignatureMethod
  swpJjcRdfC14N-rsa-sha1 . G1 swpsignature
  "..."xsdbase64Binary . _s
  foafmbox ltmailtopatrick.stickler_at_nokia.
  comgt . _s swpcertificate
  "..."xsdbase64Binary

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Publishing with Signatures - Example

• G1 Jeremy exname "Jeremy Carrol"
• G2 Chris exname "Chris Bizer"
• G3 G1 swpassertedBy G3 . G1
  swpdigestMethod swpJjcRdfC14N-sha1 . G1
  swpdigest "..."xsdbase64Binary .
• G2 swpassertedBy G3 . G2
  swpdigestMethod swpJjcRdfC14N-sha1 . G2
  swpdigest "..."xsdbase64Binary .
• G3 swpassertedBy G3 . G3
  swpsignatureMethod swpJjcRdfC14N-rsa-sha1.
  G3 swpsignature "..."xsdbase64Binary .
  G3 swpauthority _s .
• _s foafmbox ltmailtopatrick.stickler_at_nokia.c
  omgt _s swpcertificate "..."xsdbase64Binary
  

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NG4J Use Cases

• Gnowsis Semantic Desktop
• Leo Sauermann, DFKI, Germany
• Provenance tracking in a data integration
  framework
• Source Code Versioning
• Rowland Watkins, University of Southampton, UK
• Relation and provenance tracking of source code
  changes
• SWED Semantic Web Environmental Directory
• SWAD-Europe, HP Labs and ILRT
• Provenance tracking in a data integration
  framework
• Ontology Evolution in Live Science
• Chris Catton, University of Oxford, UK
• Tracking of concept evolution and paradigm shifts
• TriQL.P Trust Architecture
• Chris Bizer, Freie Universität Berlin, Germany
• Filtering information using different trust
  policies

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So, whats the holy grail?

• Reification ?
• Quads ?
• Named Graphs ?
• RDF Dataset ?

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Thanks -)

• Named Graph Website
• Links to TriX, TriG, TriQL, RDFQ Specs
• http//www.w3.org/2004/03/trix/
• Named Graphs, Provenance and Trust
• Carroll, Bizer, Hayes and Stickler
• http//www.hpl.hp.com/techreports/2004/HPL-2004-57
  .html
• NG4J - Named Graphs API for Jena
• http//www.wiwiss.fu-berlin.de/suhl/bizer/ng4j/