reasoning and querying for the web urq.deri.ie

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


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

L


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>


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


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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foaf:knows

axel


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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foaf:knows

axel


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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foaf:knows

axel


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://exa,org/myAddrbook/Stefan_Decker “Stefan”vCard:Given

“Decker”vCard:Family


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!


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


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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reasoning and querying for the web urq.deri.ie

Documents

p foaf

web of data

display foaf data

xsparql foaf

person foaf

foaf geo

domain foaf

geo data