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The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Linked Data Like It or Loathe It? Peter F. Patel-Schneider

April 11, 2012

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Abstract

Linked Data was supposed to be “the Semantic Web done right�, at least according to Tim Berners-Lee. But just what is Linked Data? How is Linked Data different from the Semantic Web? Is Linked Data really a better way to add semantics to the web, or is it just a way to throw data out on the Web in a way that can be used in hacks? There are some signs that some order is coming to Linked Data, but is this just doing (or redoing) the work that remains 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 Web Linked Data Digging Deeper into Linked Data Final Words

Abstract

Linked Data was supposed to be “the Semantic Web done right�, at least according to Tim Berners-Lee. But just what is Linked Data? How is Linked Data different from the Semantic Web? Is Linked Data really a better way to add semantics to the web, or is it just a way to throw data out on the Web in a way that can be used in hacks? There are some signs that some order is coming to Linked Data, but is this just doing (or redoing) the work that remains 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 Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

The Semantic Web

Tim Berners-Lee’s initial vision of the web was much more than just browsers, and included a notion of a web of data with a well-defined meaning This vision as come to be known as the Semantic Web, but the “Visual” Web took off much faster and is much better known The Semantic Web is supposed to be a web of information that can be combined and processed by machines with as little direct human intervention as possible

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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:Ian e.g., pfps:Peter foaf:age "57"^^xsd:int e.g., pfps:Peter rdf:type foaf:Person Subjects, predicates, and objects are names (URIs or anonymous 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, emphasizing accessibility in the Semantic Web

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Data Alone is Insufficient

Given that Alex has heart disease ex:Alex hasDisease ex:d1 ex: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 heart disease and circulatory disease

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Data Alone is Insufficient

Given that Alex has heart disease ex:Alex hasDisease ex:d1 ex: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 heart disease and circulatory disease

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 Semantic Web. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Semantic Web. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Using Ontologies Given that Alex has heart disease ex:Alex hasDisease d1 d1 ∈ HeartDisease

And ontology information about anatomy and diseases, containing Heart v MuscularOrgan u ∃isPartOf .CirculatorySystem HeartDisease ≡ Disease u ∃affects.Heart CirculatoryDisease ≡ Disease u ∃affects.(∃isPartOf .CirculatorySystem)

Who has circulatory disease? Find ?who hasDisease ?disease ?disease ∈ CirculatoryDisease Answer: ex:Alex has circulatory disease

Is heart disease a specialization of circulatory disease? Is HeartDisease v CirculatoryDisease Answer: Yes Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Using Ontologies Given that Alex has heart disease ex:Alex hasDisease d1 d1 ∈ HeartDisease

And ontology information about anatomy and diseases, containing Heart v MuscularOrgan u ∃isPartOf .CirculatorySystem HeartDisease ≡ Disease u ∃affects.Heart CirculatoryDisease ≡ Disease u ∃affects.(∃isPartOf .CirculatorySystem)

Who has circulatory disease? Find ?who hasDisease ?disease ?disease ∈ CirculatoryDisease Answer: ex:Alex has circulatory disease

Is heart disease a specialization of circulatory disease? Is HeartDisease v CirculatoryDisease Answer: Yes Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Using Ontologies Given that Alex has heart disease ex:Alex hasDisease d1 d1 ∈ HeartDisease

And ontology information about anatomy and diseases, containing Heart v MuscularOrgan u ∃isPartOf .CirculatorySystem HeartDisease ≡ Disease u ∃affects.Heart CirculatoryDisease ≡ Disease u ∃affects.(∃isPartOf .CirculatorySystem)

Who has circulatory disease? Find ?who hasDisease ?disease ?disease ∈ CirculatoryDisease Answer: ex:Alex has circulatory disease

Is heart disease a specialization of circulatory disease? Is HeartDisease v CirculatoryDisease Answer: Yes Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Making the Semantic Web Work—Ontologies OWL (and RDFS) provide ontologies for the Semantic Web Ontologies provide machine-processable meanings for (the names in) the data, particularly the categories and relationships Ontologies admit deduction of implicit information Humans also do this (but perhaps in very different ways)

Distributed and decentralized nature of (Semantic) Web means that data sources often have differing amounts of information in different sources vocabulary shifts varying specificity

Ontologies help overcome problems in all of these Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 web documents Applications access and load documents into reasoners, which determine implicit consequences

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 web documents Applications access and load documents into reasoners, which determine implicit consequences

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

Any Role for Linked Data?

We appear to have managed to build a viable artifact without explicitly appealing to “Linked Data� Where is the need for anything more? Maybe there is a need for tying Semantic Web documents together, beyond that provided by global names

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Any Role for Linked Data?

We appear to have managed to build a viable artifact without explicitly appealing to “Linked Data� Where is the need for anything more? Maybe there is a need for tying Semantic Web documents together, beyond that provided by global names

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Any Role for Linked Data?

We appear to have managed to build a viable artifact without explicitly appealing to “Linked Data� Where is the need for anything more? Maybe there is a need for tying Semantic Web documents together, beyond that provided by global names

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Missing from the Semantic Web? Some early versions of 2004 RDF documents had a section on social 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 retrieving and 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 Web Linked Data Digging Deeper into Linked Data Final Words

Missing from the Semantic Web? Some early versions of 2004 RDF documents had a section on social 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 retrieving and 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 Web Linked Data Digging Deeper into Linked Data Final Words

RDFS Links RDFS has two properties that might be used to link documents together rdfs:isDefinedBy, e.g., http://www.whitehouse.gov/pres43 rdfs:isDefinedBy http://www.whitehouse.gov/pres41.rdf a link to something that provides a definition

rdfs:seeAlso, e.g., http://www.whitehouse.gov/pres43 rdfs:seeAlso http://www.whitehouse.gov/pres41.rdf a link to something that provides additional information

This provides a way of providing defining information that is not necessarily coupled with retrieval using the RDF identifier itself Also, there is no requirement to using the defining or additional information Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

OWL Imports, or explicit following When using OWL, you very often want to combine information from several documents One or more documents with base facts (in RDF) Documents that contain the ontologies needed to give meaning to the identifiers used

Even ontologies often should be written down in multiple documents, e.g., ontology for anatomy and ontology for diseases in different documents OWL imports is a construct that explicitly says to use information from another (web) document, e.g, the disease ontology imports the anatomy ontology Was rather controversial(!), but was adopted into OWL recommendations Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

OWL Imports, or explicit following OWL imports can be used to replace “follow your nose�, but is more general Instead of (blindly) following your nose, use OWL imports only when following links is appropriate OWL imports can be used to import from any other document Applications no longer have to explicitly load up all required documents, but can use OWL imports to gather together collections of documents that form an entire ontology (or just contain relevant data) Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

OWL Imports, or explicit following OWL imports can be used to replace “follow your nose�, but is more general Instead of (blindly) following your nose, use OWL imports only when following links is appropriate OWL imports can be used to import from any other document Applications no longer have to explicitly load up all required documents, but can use OWL imports to gather together collections of documents that form an entire ontology (or just contain relevant data) Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

OWL Imports, or explicit following OWL imports can be used to replace “follow your nose�, but is more general Instead of (blindly) following your nose, use OWL imports only when following links is appropriate OWL imports can be used to import from any other document Applications no longer have to explicitly load up all required documents, but can use OWL imports to gather together collections of documents that form an entire ontology (or just contain relevant data) Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Linking in the Semantic Web

Even without RDF social meaning, there are good ways of linking between Semantic Web documents In OWL, imports provides linking when the use of the linked information is required RDFS provides two kinds of linking in cases where use is not mandated There is no bar to using follow-your-nose when it is possible and reasonable

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 in Linked Data . . . as opposed to what is actually available as Linked Data

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

What is Linked Data? From www.w3.org/DesignIssues/LinkedData The four rules of linked data 1 2 3 4

Use URIs as names for things Use HTTP URIs so that people can look up those names When someone looks up a URI, provide useful information 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 Web Linked Data Digging Deeper into Linked Data Final Words

What is Linked Data? From www.w3.org/DesignIssues/LinkedData The four rules of linked data 1 2 3 4

Use URIs as names for things Use HTTP URIs so that people can look up those names When someone looks up a URI, provide useful information 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 Web Linked Data Digging Deeper into Linked Data Final Words

What is Linked Data? From www.w3.org/DesignIssues/LinkedData The four rules of linked data 1 2 3 4

Use URIs as names for things Use HTTP URIs so that people can look up those names When someone looks up a URI, provide useful information 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 Web Linked Data Digging Deeper into Linked Data Final 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 licence Emphasis on interlinking Providing useful information via name lookup

Is Linked Data just a way of recovering informal meaning for RDF? Instead of requiring follow-your-nose, just put it out there Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 perhaps were 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 supporting quick and dirty data mash-ups. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 supporting quick and dirty data mash-ups. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 even workshops on it (Linked Open Data Workshops)

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 even workshops on it (Linked Open Data Workshops)

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

Linking Open Data Cloud

Linking Open Data cloud diagram of 2007-05-01, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/ Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 data http://events.linkeddata.org/ldow2012/

Can’t just dismiss Linked Data

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 ontology information Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

The Problem with Linked Data It is not that linking data is not useful—it is, but the linked data story 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 the big problems, but nothing in the analysis or solution is specific to linked data. Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final 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 usable without direct human control.

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

Reasoning for Linked Data Maybe full ontology reasoning is just too hard at Linked Data scale. Perhaps look at what ontology constructs are used in Linked Data 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 use of OWL constructs Mostly single-triple constructs

Define new OWL profile (OWL LD) with only the constructs with 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 Web Linked Data Digging Deeper into Linked Data Final Words

Combining Linked Data and the Semantic Web

Good parts of Linked Data . . . publish data nicely use other’s identifiers

. . . plus good parts of Semantic Web use RDF and OWL ontologies to describe data ontologies to bridge between vocabularies OWL 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 Web Linked Data Digging Deeper into Linked Data Final Words

Combining Linked Data and the Semantic Web

Good parts of Linked Data . . . publish data nicely use other’s identifiers

. . . plus good parts of Semantic Web use RDF and OWL ontologies to describe data ontologies to bridge between vocabularies OWL 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 Web Linked Data Digging Deeper into Linked Data Final 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 Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Like or Loathe? Perhaps the effect of Linked Data is to move attention away from semantic issues towards data issues Loathe (a lot)

Perhaps Linked Data is just something for hackers to hang their hat on, since the Semantic Web has gotten semantics Loathe

Perhaps Linked Data is just a marketing slogan, and it is really just the Semantic Web itself, in disguise Loathe

Perhaps Linked Data is a buzzword of the past and has been overtaken by big data (whatever that is) Like ,

Perhaps Linked data is an honest attempt to get people to pay attention to a neglected part of the Semantic Web Like, but where is the evidence that this part was actually neglected? Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Future Work

Analysis of all the data in the Linked Data Cloud (or all the crawlable RDF in the Semantic Web) What constructs are used? What ontologies are there?

Should there be a language (and reasoner) for the Semantic Web 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?


The Semantic Web Linked Data Digging Deeper into Linked Data Final Words

Questions?

Peter F. Patel-Schneider

Linked Data Like It or Loathe It?


UK Ontology Network  

UK Ontology Network

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