The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linked DataLike It or Loathe It?
Peter F. Patel-Schneider
April 11, 2012
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Abstract
Linked Data was supposed to be “the Semantic Web done right”,at least according to Tim Berners-Lee. But just what is LinkedData? How is Linked Data different from the Semantic Web? IsLinked Data really a better way to add semantics to the web, or isit just a way to throw data out on the Web in a way that can beused in hacks? There are some signs that some order is coming toLinked Data, but is this just doing (or redoing) the work thatremains to be done (has been done) in the Semantic Web?
Warning: This is a personal view of Linked Data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Abstract
Linked Data was supposed to be “the Semantic Web done right”,at least according to Tim Berners-Lee. But just what is LinkedData? How is Linked Data different from the Semantic Web? IsLinked Data really a better way to add semantics to the web, or isit just a way to throw data out on the Web in a way that can beused in hacks? There are some signs that some order is coming toLinked Data, but is this just doing (or redoing) the work thatremains to be done (has been done) in the Semantic Web?
Warning: This is a personal view of Linked Data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Outline
1 The Semantic Web
2 Linked Data
3 Digging Deeper into Linked Data
4 Final Words
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Table of Contents
1 The Semantic Web
2 Linked Data
3 Digging Deeper into Linked Data
4 Final Words
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Semantic Web
Tim Berners-Lee’s initial vision of the web was much morethan just browsers, and included a notion of a web of datawith a well-defined meaning
This vision as come to be known as the Semantic Web, butthe “Visual” Web took off much faster and is much betterknown
The Semantic Web is supposed to be a web of informationthat can be combined and processed by machines with aslittle direct human intervention as possible
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Data
Data in the Semantic Web is written as RDF triples
An RDF triple consists of a subject, a predicate, and an object
e.g., pfps:Peter foaf:knows ox:Iane.g., pfps:Peter foaf:age "57"^^xsd:inte.g., pfps:Peter rdf:type foaf:PersonSubjects, predicates, and objects are names (URIs oranonymous names) or literals (i.e., data values)
URIs are global names, which can be used anywhere,emphasizing connections within the Semantic Web
RDF triples are available in Web documents, emphasizingaccessibility in the Semantic Web
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Data Alone is Insufficient
Given that Alex has heart disease
ex :Alex hasDisease ex :d1ex :d1 rdf :type HeartDisease
Who has circulatory disease?
?who hasDisease ?disease?disease rdf :type CirculatoryDisease
No one can be determined to have a circulatory disease
. . . because there is no connection in the data between heartdisease and circulatory disease
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Data Alone is Insufficient
Given that Alex has heart disease
ex :Alex hasDisease ex :d1ex :d1 rdf :type HeartDisease
Who has circulatory disease?
?who hasDisease ?disease?disease rdf :type CirculatoryDisease
No one can be determined to have a circulatory disease
. . . because there is no connection in the data between heartdisease and circulatory disease
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
What’s Missing: Ontologies
Ontologies
Model some portion of the world
e.g., anatomy, aircraft engines, cell phones
Introduce a vocabulary
e.g., organs, muscles, heart, diseases
Specify meaning of vocabulary
e.g., a heart is a muscular organ in the circulatory sytem
All in a formal language (a logic)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Sample Ontology Fragments
The heart is a muscular part of the circulatory system
Heart v MuscularOrgan u ∃isPartOf .CirculatorySystem
Heart disease is a disease of the heart
HeartDisease ≡ Disease u ∃affects.Heart
Circulatory disease is a disease of a part of the circulatory sys.
CirculatoryDisease ≡Disease u ∃affects.(∃isPartOf .CirculatorySystem)
Note that the syntax here is not the syntax used in the SemanticWeb.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Sample Ontology Fragments
The heart is a muscular part of the circulatory system
Heart v MuscularOrgan u ∃isPartOf .CirculatorySystem
Heart disease is a disease of the heart
HeartDisease ≡ Disease u ∃affects.Heart
Circulatory disease is a disease of a part of the circulatory sys.
CirculatoryDisease ≡Disease u ∃affects.(∃isPartOf .CirculatorySystem)
Note that the syntax here is not the syntax used in the SemanticWeb.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Using Ontologies
Given that Alex has heart diseaseex :Alex hasDisease d1d1 ∈ HeartDisease
And ontology information about anatomy and diseases,containing
Heart v MuscularOrgan u ∃isPartOf .CirculatorySystemHeartDisease ≡ Disease u ∃affects.HeartCirculatoryDisease ≡
Disease u ∃affects.(∃isPartOf .CirculatorySystem)
Who has circulatory disease?Find ?who hasDisease ?disease
?disease ∈ CirculatoryDiseaseAnswer: ex :Alex has circulatory disease
Is heart disease a specialization of circulatory disease?Is HeartDisease v CirculatoryDiseaseAnswer: Yes
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Using Ontologies
Given that Alex has heart diseaseex :Alex hasDisease d1d1 ∈ HeartDisease
And ontology information about anatomy and diseases,containing
Heart v MuscularOrgan u ∃isPartOf .CirculatorySystemHeartDisease ≡ Disease u ∃affects.HeartCirculatoryDisease ≡
Disease u ∃affects.(∃isPartOf .CirculatorySystem)
Who has circulatory disease?Find ?who hasDisease ?disease
?disease ∈ CirculatoryDiseaseAnswer: ex :Alex has circulatory disease
Is heart disease a specialization of circulatory disease?Is HeartDisease v CirculatoryDiseaseAnswer: Yes
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Using Ontologies
Given that Alex has heart diseaseex :Alex hasDisease d1d1 ∈ HeartDisease
And ontology information about anatomy and diseases,containing
Heart v MuscularOrgan u ∃isPartOf .CirculatorySystemHeartDisease ≡ Disease u ∃affects.HeartCirculatoryDisease ≡
Disease u ∃affects.(∃isPartOf .CirculatorySystem)
Who has circulatory disease?Find ?who hasDisease ?disease
?disease ∈ CirculatoryDiseaseAnswer: ex :Alex has circulatory disease
Is heart disease a specialization of circulatory disease?Is HeartDisease v CirculatoryDiseaseAnswer: Yes
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Making the Semantic Web Work—Ontologies
OWL (and RDFS) provide ontologies for the Semantic Web
Ontologies provide machine-processable meanings for (thenames in) the data, particularly the categories andrelationships
Ontologies admit deduction of implicit information
Humans also do this (but perhaps in very different ways)
Distributed and decentralized nature of (Semantic) Webmeans that data sources often have
differing amounts of information in different sourcesvocabulary shiftsvarying specificity
Ontologies help overcome problems in all of these
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Semantic Web History
Semantic Web recommendations from W3C:
1999 RDF (abstract data version)—data
2000 RDFS—very simple ontologies
2004 RDF and RDFS (logic version)
2004 OWL—general ontologies
2008 SPARQL—query language
2009 OWL 2
2012 SPARQL 1.1
2012? RDF extension
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Semantic Web (recap)
RDF is used to write data, in the form of triples
OWL (and RDFS) provide ontology support
Global names provide connections
Semantic Web data and ontologies are accessible as webdocuments
Applications access and load documents into reasoners, whichdetermine implicit consequences
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Semantic Web (recap)
RDF is used to write data, in the form of triples
OWL (and RDFS) provide ontology support
Global names provide connections
Semantic Web data and ontologies are accessible as webdocuments
Applications access and load documents into reasoners, whichdetermine implicit consequences
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Table of Contents
1 The Semantic Web
2 Linked Data
3 Digging Deeper into Linked Data
4 Final Words
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Any Role for Linked Data?
We appear to have managed to build a viable artifact withoutexplicitly appealing to “Linked Data”
Where is the need for anything more?
Maybe there is a need for tying Semantic Web documentstogether, beyond that provided by global names
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Any Role for Linked Data?
We appear to have managed to build a viable artifact withoutexplicitly appealing to “Linked Data”
Where is the need for anything more?
Maybe there is a need for tying Semantic Web documentstogether, beyond that provided by global names
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Any Role for Linked Data?
We appear to have managed to build a viable artifact withoutexplicitly appealing to “Linked Data”
Where is the need for anything more?
Maybe there is a need for tying Semantic Web documentstogether, beyond that provided by global names
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Missing from the Semantic Web?
Some early versions of 2004 RDF documents had a section onsocial meaning, including
Defining Information
The defining information for an RDF identifier, e.g.,http://www.whitehouse.gov/pres43, should available as an(RDF) document retrievable from that URI (fragment)
Follow Your Nose
Using an RDF identifier, e.g.,http://www.whitehouse.gov/pres43, commits you to retrievingand using its defining information
Softened and then removed from RDF specifications after outcry
What if document includes irrelevant information?
What if document includes controversial information?
How can you dispute defining information?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Missing from the Semantic Web?
Some early versions of 2004 RDF documents had a section onsocial meaning, including
Defining Information
The defining information for an RDF identifier, e.g.,http://www.whitehouse.gov/pres43, should available as an(RDF) document retrievable from that URI (fragment)
Follow Your Nose
Using an RDF identifier, e.g.,http://www.whitehouse.gov/pres43, commits you to retrievingand using its defining information
Softened and then removed from RDF specifications after outcry
What if document includes irrelevant information?
What if document includes controversial information?
How can you dispute defining information?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
RDFS Links
RDFS has two properties that might be used to linkdocuments together
rdfs:isDefinedBy, e.g., http://www.whitehouse.gov/pres43rdfs:isDefinedBy http://www.whitehouse.gov/pres41.rdf
a link to something that provides a definition
rdfs:seeAlso, e.g., http://www.whitehouse.gov/pres43rdfs:seeAlso http://www.whitehouse.gov/pres41.rdf
a link to something that provides additional information
This provides a way of providing defining information that isnot necessarily coupled with retrieval using the RDF identifieritself
Also, there is no requirement to using the defining oradditional information
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
OWL Imports, or explicit following
When using OWL, you very often want to combineinformation from several documents
One or more documents with base facts (in RDF)Documents that contain the ontologies needed to givemeaning to the identifiers used
Even ontologies often should be written down in multipledocuments, e.g., ontology for anatomy and ontology fordiseases in different documents
OWL imports is a construct that explicitly says to useinformation from another (web) document, e.g, the diseaseontology imports the anatomy ontology
Was rather controversial(!), but was adopted into OWLrecommendations
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
OWL Imports, or explicit following
OWL imports can be used to replace “follow your nose”, butis more general
Instead of (blindly) following your nose, use OWL importsonly when following links is appropriate
OWL imports can be used to import from any otherdocument
Applications no longer have to explicitly load up all requireddocuments, but can use OWL imports to gather togethercollections of documents that form an entire ontology (or justcontain relevant data)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
OWL Imports, or explicit following
OWL imports can be used to replace “follow your nose”, butis more general
Instead of (blindly) following your nose, use OWL importsonly when following links is appropriate
OWL imports can be used to import from any otherdocument
Applications no longer have to explicitly load up all requireddocuments, but can use OWL imports to gather togethercollections of documents that form an entire ontology (or justcontain relevant data)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
OWL Imports, or explicit following
OWL imports can be used to replace “follow your nose”, butis more general
Instead of (blindly) following your nose, use OWL importsonly when following links is appropriate
OWL imports can be used to import from any otherdocument
Applications no longer have to explicitly load up all requireddocuments, but can use OWL imports to gather togethercollections of documents that form an entire ontology (or justcontain relevant data)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linking in the Semantic Web
Even without RDF social meaning, there are good ways oflinking between Semantic Web documents
In OWL, imports provides linking when the use of the linkedinformation is required
RDFS provides two kinds of linking in cases where use is notmandated
There is no bar to using follow-your-nose when it is possibleand reasonable
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Emergence of Linked Data
Linked Open Data
“Semantic web done right”“Paradigm shift all over again”(www.w3.org/2008/Talks/0617-lod-tbl)
Many documents provide quick introductions to Linked Data
Provide a view of what its originators believe is important inLinked Data
. . . as opposed to what is actually available as Linked Data
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
What is Linked Data?
From www.w3.org/DesignIssues/LinkedData
The four rules of linked data1 Use URIs as names for things2 Use HTTP URIs so that people can look up those names3 When someone looks up a URI, provide useful information4 Include links to other URIs, so that they can discover more
things
Five Star Linked Open Data
? Available on the web with an open licence?? Available as machine-readable structured data
? ? ? Available in a non-proprietary format? ? ?? Use open standards from W3C (RDF and SPARQL) to identify
things, so that people can point at your stuff? ? ? ? ? Link your data to other people’s data to provide context
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
What is Linked Data?
From www.w3.org/DesignIssues/LinkedData
The four rules of linked data1 Use URIs as names for things2 Use HTTP URIs so that people can look up those names3 When someone looks up a URI, provide useful information4 Include links to other URIs, so that they can discover more
things
Five Star Linked Open Data
? Available on the web with an open licence?? Available as machine-readable structured data
? ? ? Available in a non-proprietary format? ? ?? Use open standards from W3C (RDF and SPARQL) to identify
things, so that people can point at your stuff? ? ? ? ? Link your data to other people’s data to provide context
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
What is Linked Data?
From www.w3.org/DesignIssues/LinkedData
The four rules of linked data1 Use URIs as names for things2 Use HTTP URIs so that people can look up those names3 When someone looks up a URI, provide useful information4 Include links to other URIs, so that they can discover more
things
Five Star Linked Open Data
? Available on the web with an open licence?? Available as machine-readable structured data
? ? ? Available in a non-proprietary format? ? ?? Use open standards from W3C (RDF and SPARQL) to identify
things, so that people can point at your stuff? ? ? ? ? Link your data to other people’s data to provide context
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
What’s New in Linked Data?
Not using URIs as names—that’s required by RDF
Not using HTTTP URIs as names—that was normal
Not interlinking—that was normal
Not machine-readable—that’s required by RDF
Not non-proprietary—that’s RDF
Not open standards—that’s RDF
Perhaps
Open licenceEmphasis on interlinkingProviding useful information via name lookup
Is Linked Data just a way of recovering informal meaning forRDF?
Instead of requiring follow-your-nose, just put it out there
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Liking Linked Data—Initial View
Linked Data requires
combining RDF data from various (web) sources and
agreeing to use non-local identifiers
which are both laudable aspects of the Semantic Web, but perhapswere underemphasized.
Linked Data
encourages, but does not require, follow your nose
combines (simple) data from multiple sources
so that simple applications can be quickly built.
Linked Data is a hacker’s version of the Semantic Web supportingquick and dirty data mash-ups.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Loathing Linked Data—Initial View
Linked Data ignores
distinctions between data sources and ontology sources
issues with trust and consistency
which should both be aspects of the Semantic Web.
Linked Data
follows your nose, but when and where to?
doesn’t specify which language is to be used
requiring close control when building applications.
Linked Data is a hacker’s version of the Semantic Web supportingquick and dirty data mash-ups.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linked Data—Initial View
There doesn’t appear to be much to Linked Data at all, only
a slight change in emphasis from the Semantic Web
a restating of follow your nose
Maybe there isn’t much Linked Data, so we shouldn’t care about it
There certainly is enough noise about Linked Data, and evenworkshops on it (Linked Open Data Workshops)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linked Data—Initial View
There doesn’t appear to be much to Linked Data at all, only
a slight change in emphasis from the Semantic Web
a restating of follow your nose
Maybe there isn’t much Linked Data, so we shouldn’t care about it
There certainly is enough noise about Linked Data, and evenworkshops on it (Linked Open Data Workshops)
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
How Big is Linked Data?
Linking Open Data Cloud lod-cloud.net
Map of major linked open RDF data sources
Currently (September 2011) 295 sources
Appears to have attracted considerable attention
What just is this measuring?
Major RDF data sources that tightly link together
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
How Big is Linked Data?
Linking Open Data Cloud lod-cloud.net
Map of major linked open RDF data sources
Currently (September 2011) 295 sources
Appears to have attracted considerable attention
What just is this measuring?
Major RDF data sources that tightly link together
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linking Open Data Cloud
Linking Open Data cloud diagram of 2007-05-01, by RichardCyganiak and Anja Jentzsch. http://lod-cloud.net/
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linking Open Data Cloud
Linking Open Data cloud diagram of 2011-09-19, ibid
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linked Data Exists
Considerable self-identified Linked Data exists
Considerable other attention has been paid to Linked Data
Lots of web sites on linked data, tutorials, talks, books, etc.Continuing workshop series on linked datahttp://events.linkeddata.org/ldow2012/
Can’t just dismiss Linked Data
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Table of Contents
1 The Semantic Web
2 Linked Data
3 Digging Deeper into Linked Data
4 Final Words
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Linked Data is Just Data
Linked Data is Merely More Data(Jain, Hitzler, Yeh, Verma, Sheth, AAAI SSS 2010)
Analysis of actual Linked Data (a few years ago)
Different data sources use different vocabularies
Different data sources use different modeling decisions
Linked Data does not describe the different data sources
Few constructs to describe the data and tie it together
Effects:
Finding data requires human control
Combining data from different sources requires human control
Useful inferences cannot be made because of missing ontologyinformation
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Ontologies in the Linked Data Story
Ontologies do get mentioned
“Ontology bits for . . . ”(www.w3.org/2008/Talks/0617-lod-tbl)Use RDFS to get lightweight ontologies(linkeddatabook.com/book)Add in equality, equivalency, and inverses from OWL (ibid)Other sources suggest different bits
. . . but not very prominently
Precise ontology language is left un(der)specified
How can this be if there is single Linked Open Data Cloud?Which ontology reasoner to use?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
The Problem with Linked Data
It is not that linking data is not useful—it is, but the linked datastory is not addressing the big problems with the Semantic Web,such as
lack of ontologies
need for better ontology tools
need for even better reasoners
lack of good methods for selecting data
lack of good methods for accessing non-RDF data
Some work that is labelled as linked data does address a few of thebig problems, but nothing in the analysis or solution is specific tolinked data.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Why is Linked Data being used?
Semantic Web requires reasoning, so it’s too hard
Semantic Web requires thought, so it’s too hard
Semantic Web requires global consistency, so it’s impossible
Semantic Web requires explicit importing of used information,so it’s too hard
. . .
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Where is the Theory of Linked Data
How to select data sources?
When to follow your nose?
Where to get ontologies?
How to recover from contradictions?
Who to trust?
All need to be addressed to make Linked Data really usablewithout direct human control.
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Where is Reasoning in Linked Data?
Need more than RDFS reasoning plus owl:sameAs
but even RDFS reasoning is hard,Can’t just say that parallelism solves the problem,need to think about what needs to be done.
Full ontology Reasoning is even harder,
but so is communication, DBs, . . .
Reasoning can be slow
but so can be communication, DBs, . . .
No reason to avoid reasoning
just need to consider its potential costs
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Reasoning for Linked Data
Maybe full ontology reasoning is just too hard at Linked Datascale.
Perhaps look at what ontology constructs are used in LinkedData and construct a reasoner for these constructs.
OWL: Yet to arrive on the Web of Data?Glimm, Hogan, Kroetzsch, Polleres LDOW 2012
Examining 2011 Billion Triple Challenge data found some useof OWL constructs
Mostly single-triple constructs
Define new OWL profile (OWL LD) with only the constructswith significant use—a subset of OWL RL
Design very fast reasoners for this profile
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Combining Linked Data and the Semantic Web
Good parts of Linked Data . . .
publish data nicelyuse other’s identifiers
. . . plus good parts of Semantic Web
use RDF and OWLontologies to describe dataontologies to bridge between vocabulariesOWL imports helps control which documents to use
But, but, but, . . . , that’s just the Semantic Web, isn’t it?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Combining Linked Data and the Semantic Web
Good parts of Linked Data . . .
publish data nicelyuse other’s identifiers
. . . plus good parts of Semantic Web
use RDF and OWLontologies to describe dataontologies to bridge between vocabulariesOWL imports helps control which documents to use
But, but, but, . . . , that’s just the Semantic Web, isn’t it?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Table of Contents
1 The Semantic Web
2 Linked Data
3 Digging Deeper into Linked Data
4 Final Words
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Like or Loathe?
Perhaps the effect of Linked Data is to move attention awayfrom semantic issues towards data issues
Loathe (a lot)
Perhaps Linked Data is just something for hackers to hangtheir hat on, since the Semantic Web has gotten semantics
Loathe
Perhaps Linked Data is just a marketing slogan, and it isreally just the Semantic Web itself, in disguise
Loathe
Perhaps Linked Data is a buzzword of the past and has beenovertaken by big data (whatever that is)
Like ,Perhaps Linked data is an honest attempt to get people topay attention to a neglected part of the Semantic Web
Like, but where is the evidence that this part was actuallyneglected?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
The Semantic WebLinked Data
Digging Deeper into Linked DataFinal Words
Future Work
Analysis of all the data in the Linked Data Cloud (or all thecrawlable RDF in the Semantic Web)
What constructs are used?What ontologies are there?
Should there be a language (and reasoner) for the SemanticWeb or for Linked Data, as they currently exist?
If so, what should the language look like?If so, how should the reasoner behave?
Peter F. Patel-Schneider Linked Data Like It or Loathe It?
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