reasoning and querying for the web urq.deri.ie
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Reasoning and Querying for the Web http://urq.deri.ie. Dr. Axel Polleres. Problem: The Web is not(!) a database. Dynamics: historical data changes, trends. . Sensors: limited resources distribution incomplete data. . RDBMS. Social Interactions: Aggregated view vs. - PowerPoint PPT PresentationTRANSCRIPT
Copyright 2009 Digital Enterprise Research Institute. All rights reserved.
Digital Enterprise Research Institute www.deri.ie
Reasoning and Querying for the Web
http://urq.deri.ieDr. Axel Polleres
Digital Enterprise Research Institute www.deri.ie
2 of URQ
Problem: The Web is not(!) a database
"If HTML and the Web made all the online documents look like one huge book, RDF, schema and inference languages will make all the data in the world look like one huge database„
Tim Berners-Lee, Weaving the Web, 1999
Database? Not quite!
RDBMS
<www>Social Interactions:
•Aggregated view vs. •privacy concerns
Dynamics:•historical data•changes, trendsSensors:
•limited resources•distribution•incomplete data
… and btw.
WWW, 10 billion+ pages going up
Still, we want an integrated view!
<XML>
<HTML>
<RDF>
RDBMS
Heterogeneity:•Health records•Digital Libraries, CMS, blogs…
CMS
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For Today – Let’s stick with mainly the first box:
0) Where is the data? 1) Formal languages & how they interplay 2) Reasoning with Web data 3) Querying Web data
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0) Prerequisite – Good news!
Thanks to UDI2, UIMR, USCS, UNLP, USM etc. we may assume to already have loads of RDF/OWL data available: Crawled from the Web, Linked Data Cloud From Semantic Desktop Mined/aggregated from Sensors Extracted by shallow NLP techniques from text Etc.
Cool, now how shall we aggregate it?
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1) Languages & how they interplay
Challenges: Querying XML & RDF: XQuery & SPARQL Ontologies & Rules: OWL2 & RIF Querying Ontologies & Rules: SPARQL/OWL+RIF
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XSPARQL: Bringing XML and RDF closer!
What if I want to translate all my RDF and OWL data back to XML?
E.g. Display FOAF data on a KML map. What to use? Custom Script? XSLT? SPARQL?
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XSPARQL: Close the gap in the Web of Data:
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<XML/>SOAP/WSDL
RSS
HTML
SPARQL
XSLT/XQuery
XS
PA
RQ
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Example: Generate KML from FOAF+Geo:
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XSPARQL+FOAF and GEO data enables KML map data:
http://www.deri.ie/Stefan_Decker#me
foaf:name
“Stefan Decker”
foaf:locatedIn
http://dbpedia.org/Galway
geo:lat
-9.041800
53.272900
geo:lat
More:http://xsparql.deri.org/spec/xsparql-use-cases.html
<kml xmlns="http://www.opengis.net/kml/2.2">{for $person $name $long $latfrom <http://www.deri.ie/Stefan_Decker>where { $person a foaf:Person; foaf:name $name; foaf:based_near [ geo:long $long; geo:lat $lat ] }return <Placemark> <name>{fn:concat("Location of ", $name)}</name> <Point> <coordinates>{fn:concat($long, ",", $lat, ",0")}</coordinates> </Point></Placemark>}</kml>
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XSPARQL “crew”
Nuno Lopes
Stefan Bischof
Alumni: Waseem Akhtar Thomas Krennwallner
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Reasoning needed!
SELECT ?N WHERE {?P foaf:Name ?N }
Returns: “Stefan Decker”
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http://www.deri.ie/Stefan_Decker#me “Stefan Decker”foaf:name
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Reasoning needed!
SELECT ?N WHERE {?P a foaf:Person; foaf:Name ?N }
Returns: nothing
Why? RDFS reasoning needed!Together with:
foaf:knows rdfs:domain foaf:PersonWe could infer that Stefan is a person…
Too bad, standard SPARQL (and XSPARQL) engines don’t do this!You may think this is easy… just add the inferred triples, but…
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http://www.deri.ie/Stefan_Decker#me “Stefan Decker”foaf:name
foaf:knows
axel
Digital Enterprise Research Institute www.deri.ie
Reasoning and SPARQL is tricky!
Let’s assume we know: Every Person who is known has a name
Cool, we can write this in OWL!
Cool, let’s do SPARQL over it! Let’s ask for names of all known Persons?
SELECT ?N { [] foaf:knows ?P. ?P foaf:name ?N }
Shouldn’t have an answer, or should it?
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http://www.deri.ie/Stefan_Decker#me “Stefan Decker”foaf:name
foaf:knows
axel
Digital Enterprise Research Institute www.deri.ie
Reasoning and SPARQL is tricky!
Let’s assume we know: Every Person who is known is has a name
Cool, we can write this in OWL!
Now how about this one: Is there a known person with a name?
ASK?N { [] foaf:knows ?P. ?P foaf:name ?N }
Hmmm, should have an answer, or shouldn’t it?
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http://www.deri.ie/Stefan_Decker#me “Stefan Decker”foaf:name
foaf:knows
axel
Digital Enterprise Research Institute www.deri.ie
RDF & OWL don’t solve heterogeneity
Example assumed we had Stefan’s data in FOAF,
but in my desktop application, I might have e.g. vCard instead:
Needs more than OWL! Rules, Alignments! E.g.:
{ ?P foaf:name ?N } :- { ?P vCard:Given ?G; vCard:Family ?F
?N = fn:concat(?G, “ “, ?F) }
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http://www.deri.ie/Stefan_Decker#me “Stefan Decker”foaf:name
http://exa,org/myAddrbook/Stefan_Decker “Stefan”vCard:Given
“Decker”vCard:Family
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Reasoning needed!
W3C SPARQL Working Group W3C OWL2 WG W3C Rule Interchange Format Working groups work on new standards to solve these issues … and more!
DERI members involved: SPARQL: Alex Passant & myself (co-chair) OWL2: Antoine Zimmermann RIF: myself
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2) Reasoning with Web Data
Challenges Authoritativeness Scale Completeness, Consistency
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Who can say what & where on the Web??
Authoritative Reasoning : Who gets to say what
FOAF spec authoritative for foaf:Person ✓ MY spec not authoritative for foaf:Person
✘
Only allow extension in authoritative documents my:Person rdfs:subClassOf foaf:Person
. (MY spec) ✓
BUT: Reduce obscure memberships foaf:Person rdfs:subClassOf my:Person
. (MY spec) ✘ ALSO: Protect specifications
foaf:mbox rdf:type owl:SymmetricProperty . (MY spec) ✘
• Linear scale for most rules• 1.1bn in => 1.1+1.9bn out• <10 hours
Ontology Hijacking18
Check our ASWC paper! Tech Report!Journal version to come at IJSWIS!
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Reasoning with Web Data
Aidan Hogan SAOR/SWSE (planned work):
– extend SAOR to support OWL2– datatype support– develop SPARQL(2) on top of SWSE– Validation of Web data
Alumni: Andreas Harth
Antoine Zimmermann Reasoning with Alignments
Gergely Lukacsy Complete DL Reasoning (OWL2) at large scale
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3) Querying Web Data
Challenges: Finding/Querying Distributed SPARQL endpoints
More ideas we currently work on: Query distributed SPARQL endpoints Querying Temporal data on the Web (e.g. Wikis,
ontologies)
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Help the end user
Challenges: End users don’t want to write RDF End users don’t speak OWL End users don’t care about SW!
How can we change this? Help users to find the right ontologies to use How to avoid the publication of messy Web data in first
place
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Help the end user: Semantic Drupal:
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Enable data mining, text-analysis, reasoning, aggregation, trend detection over different platforms
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Semantic Drupal: Populate the Web of Data Reasonably
Check prototype at: http://drupal.org/project/rdfcck
Main developer: Stéphane Corlosquet Also check our TR!
– Explains Reasoning in the background
Next Steps:– Not only export RDF from Drupal, but also allow Drupal
Sites to consume Linked Data and act as SPARQL endpoints– Ontology Term Search Engine (powered by SWSE&Sindice,
Antoine, Aidan & Renaud) for easier vocab linkage– Stéphane to conclude his MSc thesis
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What I didn’t talk about:
Projects, Collaborations Upcoming visitors
(Prof. George Vouros, Prof. Piero Bonatti) Things cooking
Reasoning/Querying over heterogeneous data from DERI HCLS Domain (Ratnesh Sahay & Antoine Zimmermann)
Temporal SPARQL GiaBATA Rules and Ontology aware SPARQL engine …
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Outlook
That was some, but not ALL of the things happening in our research Unit.1) Formal languages & how they interplay
2) Reasoning with Web data
3) Querying Web data
If you have questions on SW standards! If you have questions about Reasoning& Querying
techniques on RDF/OWL/RIF You are welcome to ask us!
Let’s deploy the Semantic Web reasonably!
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