semantic web: the inside story
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Tetherless World Constellation
Semantic Web:The Inside Story
Jim Hendler@jahendler
Tetherless World Professor of Computer, Web and Cognitive ScienceDirector, Rensselaer Institute for Data Exploration and Applications
Rensselaer Polytechnic Institute
http://www.cs.rpi.edu/~hendler
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Original Outline (July 2000)
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History
>250 Semantic Web talks since 2000
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On the Web -- links are critical!
<a href= URI>
HTML
Web page Any Web Resource
<a href=“http://…”>
RDF
URI URI
URI
RDF is like the web!
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<mind:Person rdf:id=“Hendler”> <mind:title jobs:Professor> <jobs:placeOfWork http://www.cs.rpi.edu></mind:Person>
DOC1
HendlerDOC1 Mind:title
Jobs:placeOfWork Web Pagehttp://www…
ProfessorJobs:Mind:
Jobs:
Links in the data
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<mind:Person rdf:id=“Hendler”> owl:sameAs<http://dbpedia.org/page/James_Hendler>
DOC2
HendlerMind:title
Jobs:placeOfWork Web Pagehttp://www…
Jobs:Professor
Asserting Links in the data
Dbpedia:Hendler
Owl:sameAs
Dbpedia:ComputerScientist
Dbpedia:occupation
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Linking Web Resources
Sindice.com
8NCARAI, Apr 2002
Ontologies can help
Catalog/ID
GeneralLogical
constraints
Terms/glossary
Thesauri“narrower
term”relation
Formalis-a
Frames(properties)
Informalis-a
Formalinstance Value
Restrs.
Disjointness, Inverse, part-
of…
TAXONOMY ONTOLOGY
(McGuinness, 99)
9NCARAI, Apr 2002
Ontologies can help
Catalog/ID
GeneralLogical
constraints
Terms/glossary
Thesauri“narrower
term”relation
Formalis-a
Frames(properties)
Informalis-a
Formalinstance Value
Restrs.
Disjointness, Inverse, part-
of…
TAXONOMY ONTOLOGY
(McGuinness, 99)
But is this the right view?
Ontology: the OWL DL view
• Ontology as Barad-Dur (Sauron's tower):– Extremely powerful!
– Patrolled by Orcs• Let one little hobbit
in, and the whole thing could come crashing down
inconsistency
Decidable Logic basis
ROI: Reasoning over (Enterprise) data
• This "big O" Ontology finds use cases in verticals and enterprises– Where the vocabulary can be controlled– Where finding things in the data is important
• Example– Drug discovery from data
• Model the molecule (site, chemical properties, etc) as faithfully and expressively as possible
• Use "Realization" to categorize data assets against the ontology– Bad or missed answers are money down the drain
ontology: the Linked Data view
• ontology and the tower of Babel– We will build a tower
to reach the sky– We only need a little
ontological agreement
• Who cares if we all speak different languages?
Genesis 11:7 Let us go down, and there confound their language, that they may not understand one another's speech. So the Lord scattered them abroad from thence upon the face of all the earth: and they left off to build the city.
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Linked Data in many sectors
Linkeddata.org 37 billion links
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But is it getting real world acceptance?
Facebook: 2011 Oracle: 2012
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The big winner: The Knowledge Graph
Google finds embedded metadata on >20% of its crawl – Guha, 2014
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Semantic Web
• What is driving the change?– Maturation of Linked Data
technologies•Embedded markup
– Schema.org & RDFa •SPARQL endpoints
– graph database standard•Lightweight Knowledge
– A little semantics goes a long way
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Linked Data + Semantics
• "Linked Data" approach finds its use cases in Web Applications (at Web scales)– A lot of data, a
little semantics– Finding anything
in the mess can be a win!
http://www.cs.rpi.edu/~hendler/LittleSemanticsWeb.html
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Semantic Search
IEEE Computer, Jan 2010)
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Contenders ca. 2010
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Google 2009
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Google 2012
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Google 2013
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• The schema.org hierarchy and details are all available on line
–https://schema.org/docs/full.html
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• Why the change from learning to human markup enhanced?
© Peter Mika, 2014.
© Peter Mika, 2014.
© Peter Mika, 2014.
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similar story for Facebook
2012: Extending the Social Graph
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Some others
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The gap is growing
• Linked-Data-based applications are growing in size, number and importance on the Web– But the “vocabulary” story is still
unclear• Ontology research is turning OWL
into a usable KR standard,– But the linking story is still unclear
No linking without vocabulariesNo network effect without links
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What I think we MUST do
• Bridging the gap between the linked-data and ontology views requires some key research challenges to be addressed– DL (and FOL) are useful formalisms for
KR&R, but do not address the needs of the Web!
– Empirical comparisons are useful in scaling systems, but do not address the needs of an academic community!
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My Challenge to you
• A sufficient formalism for Semantic Web applications must– Provide a model that accounts for linked
data • What is the equivalent of a DB calculus?
– Provide a means for evaluating incomplete reasoners • In practice we must be able to model A-box
effects as formally as T-box technologies
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Be bold!
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Summary
• The Semantic Web, whether as “linked data” or vocabularies in usage is getting significant use.– in many of the largest web players
• But there’s much more work to do– improving semantics in many applications– exploring appropriate business models
• Academic research remains an exciting area– much is extending formalization or faster queries – some big questions still remain
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