Introduction to the Semantic Web - phpCE 2017

Video recording: https://www.youtube.com/watch?v=WUOuKB0Ji10.
Joind.in: https://joind.in/talk/eb31e

What if we could evolve our web of individual documents and data to a web of interlinked knowledge, a web where machines can automatically combine data from multiple sources and draw conclusions from it?
The Semantic Web technologies from W3C enable us to make sense of the data wilderness on the web and unlock the full potential of the data treasures hidden in it. In this talk, we will see how RDF enables us to formally describe the meaning of data and how such data can be queried with SPARQL. We will look at how OWL lets us make more expressive statements about the world, so that a computer can logically reason about it and infer new information. We will demonstrate these technologies by showing how they can be used to combine data sets in different formats as if they were one and letting a computer draw logical (and perhaps surprising) conclusions for us.

Transcript

1. Introduction to the Semantic Web @arnoutboks Arnout Boks #phpce17 04 nov 2017
2. @arnoutboks #phpce17 What this talk is NOT about…
3. @arnoutboks #phpce17 Finding info on the web An example
4. @arnoutboks #phpce17 “Web 1.0”
5. @arnoutboks #phpce17 “Web 1.0”
6. @arnoutboks #phpce17 “Web 1.0”
7. @arnoutboks #phpce17 Web 1.0 Web of Documents for human consumption
8. @arnoutboks #phpce17 “Web 2.0” Feed of events • iCalendar or vCalendar? • Different types of events?
9. @arnoutboks #phpce17 “Web 2.0” Weather forecast API • XML or JSON? • Which fields and properties? • Which units?
10. @arnoutboks #phpce17 Web 2.0 Web of (individual) API’s for consumption by specialized software
11. @arnoutboks #phpce17 Semantic web • Question to agent (e.g. Siri) • Agent searches across different sources • Agent combines data • Agent answers question
12. @arnoutboks #phpce17 Semantic Web (“Web 3.0”?) Web of Linked Data for consumption by intelligent agents/PA’s
13. @arnoutboks #phpce17 Revolutionary? Term coined by Tim Berners-Lee in 2001
14. @arnoutboks #phpce17 Revolutionary? Based on W3C-standards • RDF (1998) • RDFS (1998) • SPARQL (2008) • OWL (2004) • …
15. @arnoutboks #phpce17 RDF Cornerstone of the Semantic Web Resource Description Framework Cornerstone of the Semantic Web
16. @arnoutboks #phpce17 Records statements about things
17. @arnoutboks #phpce17 RDF allows reading, merging, relaying and inferring statements without fully understanding them
18. @arnoutboks #phpce17 RDF (triples) Subject Predicate Object
19. @arnoutboks #phpce17 RDF (triples) Subject Predicate Object Arnout worksAt Moxio
20. @arnoutboks #phpce17 RDF (triples) Subject Predicate Object Arnout worksAt Moxio Arnout twitterHandle “@arnoutboks” Arnout livesIn Delft Delft cityIn The Netherlands Moxio basedIn Delft
21. @arnoutboks #phpce17 RDF (graph) Arnout Moxio Delft @arnoutboks worksAt basedIn The Netherlands Subject Predicate Object Arnout worksAt Moxio Arnout twitterHandle “@arnoutboks” Arnout livesIn Delft Delft cityIn The Netherlands Moxio basedIn Delft
22. @arnoutboks #phpce17 Merging RDF (triples) Subject Predicate Object Arnout worksAt Moxio Arnout twitterHandle “@arnoutboks” Arnout livesIn Delft Delft cityIn The Netherlands Moxio basedIn Delft Subject Predicate Object The Netherlands hasCapital Amsterdam The Netherlands population “17.000.000”
23. @arnoutboks #phpce17 Merging RDF (triples) Subject Predicate Object Arnout worksAt Moxio Arnout twitterHandle “@arnoutboks” Arnout livesIn Delft Delft cityIn The Netherlands Moxio basedIn Delft The Netherlands hasCapital Amsterdam The Netherlands population “17.000.000”
24. @arnoutboks #phpce17 Merging RDF (graph) Arnout Moxio Delft @arnoutboks worksAt basedIn The Netherlands Amsterdam hasCapital 17.000.000 population
25. @arnoutboks #phpce17 Serializing RDF: Turtle @prefix : <http://www.example.com/#> . @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax- ns#> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . @base <http://www.example.com/> . :Arnout :livesIn :Delft ; :worksAt :Moxio ; :twitterHandle "@arnoutboks"^^xsd:string . :Delft :cityIn :The_Netherlands . :Moxio :basedIn :Delft .
26. @arnoutboks #phpce17 Serializing RDF: RDF/XML <?xml version="1.0"?> <rdf:RDF xmlns="http://www.example.com/#" <!-- ... -->> <rdf:Description rdf:about="http://www.example.com/#Arnout"> <twitterHandle rdf:datatype="http://www.w3.org/2001/XMLSchema#string">@a rnoutboks</twitterHandle> <worksAt rdf:resource="http://www.example.com/#Moxio"/> <livesIn rdf:resource="http://www.example.com/#Delft"/> </rdf:Description> <!-- ... --> </rdf:RDF>
27. @arnoutboks #phpce17 Serializing RDF: JSON-LD [ { "@id" : "http://www.example.com/#Arnout", "http://www.example.com/#livesIn" : [ { "@id" : "http://www.example.com/#Delft" } ], "http://www.example.com/#twitterHandle" : [ { "@value" : "@arnoutboks" } ], "http://www.example.com/#worksAt" : [ { "@id" : "http://www.example.com/#Moxio" } ] }, ... ]
28. @arnoutboks #phpce17 RDF is an abstract data model with different serialization formats
29. @arnoutboks #phpce17 Identity Because there are multiple things named “Amsterdam”
30. @arnoutboks #phpce17 Identity Subject Predicate Object Amsterdam numberOfGuns “42” Amsterdam status Wrecked National Maritime Museum (“Scheepvaartmuseum”)
31. @arnoutboks #phpce17 Identity Subject Predicate Object Amsterdam numberOfGuns “42” Amsterdam status Wrecked Subject Predicate Object The Netherlands hasCapital Amsterdam The Netherlands population “17.000.000” National Maritime Museum (“Scheepvaartmuseum”) Lonely Planet
32. @arnoutboks #phpce17 Identity The Netherlands Amsterdam hasCapital 17.000.000 population 42 Wrecked
33. @arnoutboks #phpce17 URI’s for namespacing National Maritime Museum (“Scheepvaartmuseum”) https://www.hetscheepvaartmuseum.nl/ships/Amsterdam https://www.hetscheepvaartmuseum.nl/ships/numberOfGuns Lonely Planet https://www.lonelyplanet.com/Amsterdam https://www.lonelyplanet.com/hasCapital
34. @arnoutboks #phpce17 Prefixes & QNames lonelyplanet:Amsterdam === https://www.lonelyplanet.com/Amsterdam QName URI local name local name namespace prefix
35. @arnoutboks #phpce17 Prefixes & QNames National Maritime Museum (“Scheepvaartmuseum”) nmm:Amsterdam nmm:numberOfGuns Lonely Planet lonelyplanet:Amsterdam lonelyplanet:hasCapital
36. @arnoutboks #phpce17 Three fundamental laws of the (Semantic) Web
37. @arnoutboks #phpce17 Different name, different concept? lonelyplanet-en:Brussels lonelyplanet-nl:Brussel lonelyplanet-fr:Bruxelles lonelyplanet-zh:布魯塞爾
38. @arnoutboks #phpce17 Different name, different concept? mi6:007 mi6:JamesBond
39. @arnoutboks #phpce17 Nonunique Naming Assumption Different names do not imply different concepts
40. @arnoutboks #phpce17 Truth & authority Subject Predicate Object whitehouse:Obama nsa:tapped whitehouse:Trump Donald Trump
41. @arnoutboks #phpce17 Truth & authority Subject Predicate Object php-fig:CakePHP fw:isBetterThan php-fig:Symfony Donald Trump
42. @arnoutboks #phpce17 The AAA Slogan “[On the web] Anyone can say Anything about Any topic”
43. @arnoutboks #phpce17 (this slide intentionally left blank)
44. @arnoutboks #phpce17 Absence of information Subject Predicate Object whitehouse:Trump fw:knows php-fig:Symfony whitehouse:Trump fw:knows php-fig:CakePHP whitehouse:Trump fw:knows php-fig:CodeIgniter
45. @arnoutboks #phpce17 Open World Assumption We never have all information
46. @arnoutboks #phpce17 SPARQL Query language for Semantic Web data
47. @arnoutboks #phpce17 Triple Store Database for RDF triples
48. @arnoutboks #phpce17 SPARQL SELECT ?employee ?company WHERE { ?employee :worksAt ?company . ?company :basedIn :Delft . }
49. @arnoutboks #phpce17 SPARQL SELECT ?employee ?company WHERE { ?employee :worksAt ?company . ?company :basedIn :Delft . } ?employee ?company :Arnout :Moxio
50. @arnoutboks #phpce17 SPARQL SELECT ?employee ?company ?city WHERE { ?employee :worksAt ?company . ?company :basedIn ?city . ?employee :livesIn ?city . } ?employee ?company ?city :Arnout :Moxio :Delft
51. @arnoutboks #phpce17 Online SPARQL endpoints http://dbpedia.org/sparql
52. @arnoutboks #phpce17 Online SPARQL endpoints PREFIX dbo: <http://dbpedia.org/ontology/> PREFIX dbr: <http://dbpedia.org/resource/> SELECT ?song ?runtime WHERE { ?song dbo:artist dbr:The_Beatles . ?song dbo:runtime ?runtime . ?song rdf:type dbo:Song . } ORDER BY DESC (?runtime)
53. @arnoutboks #phpce17 Online SPARQL endpoints
54. @arnoutboks #phpce17 RDF Schema Schema language for Semantic Web data
55. @arnoutboks #phpce17 RDF Schema (RDFS) Describes the structure of RDF-data… in RDF • Classes • Properties • Domain and range of properties • Inheritance of classes • ‘Inheritance’ of properties
56. @arnoutboks #phpce17 RDF Schema (RDFS) Subject Predicate Object :DonaldTrump :isFatherOf :IvankaTrump
57. @arnoutboks #phpce17 RDF Schema (RDFS) Subject Predicate Object :DonaldTrump :isFatherOf :IvankaTrump :isFatherOf rdfs:range :Person :isFatherOf rdfs:domain :Father :Father rdfs:subclassOf :Parent :Parent rdfs:subclassOf :Person :isFatherOf rdfs:subpropertyOf :isParentOf
58. @arnoutboks #phpce17 RDF Schema & Inference Subject Predicate Object :DonaldTrump :isFatherOf :IvankaTrump :isFatherOf rdfs:range :Person :isFatherOf rdfs:domain :Father :Father rdfs:subclassOf :Parent :Parent rdfs:subclassOf :Person :isFatherOf rdfs:subpropertyOf :isParentOf :IvankaTrump rdf:type :Person :DonaldTrump rdf:type :Father :DonaldTrump rdf:type :Parent :DonaldTrump rdf:type :Person :DonaldTrump :isParentOf :IvankaTrump
59. @arnoutboks #phpce17 Inference Reasoner (asserted) triples inferred/virtual triples
60. @arnoutboks #phpce17 Inference Reasoner (asserted) triples inferred/virtual triples
61. @arnoutboks #phpce17 SPARQL & Inference SELECT ?person WHERE { ?person rdf:type :Person . } ?person :IvankaTrump :DonaldTrump
62. @arnoutboks #phpce17 Combining data using inference Subject Predicate Object a:DonaldTrump rdf:type a:Person Datasource A Subject Predicate Object b:MelaniaTrump rdf:type b:Human Datasource B
63. @arnoutboks #phpce17 Combining data using inference Subject Predicate Object a:DonaldTrump rdf:type a:Person Datasource A Subject Predicate Object b:MelaniaTrump rdf:type b:Human Datasource B Subject Predicate Object a:Person rdfs:subclassOf b:Human b:Human rdfs:subclassOf a:Person Mapping rules
64. @arnoutboks #phpce17 Combining data using inference Subject Predicate Object a:DonaldTrump rdf:type a:Person b:MelaniaTrump rdf:type b:Human a:Person rdfs:subclassOf b:Human b:Human rdfs:subclassOf a:Person a:DonaldTrump rdf:type b:Human b:MelaniaTrump rdf:type a:Person
65. @arnoutboks #phpce17 Query different sources as if they were one
66. @arnoutboks #phpce17 RDF Schema vs. JSON/XML Schema Subject Predicate Object mi6:JamesBond rdf:type mi6:SecretAgent mi6:JamesBond nmm:numberOfGuns “1” MI6 files
67. @arnoutboks #phpce17 RDF Schema vs. JSON/XML Schema Subject Predicate Object mi6:JamesBond rdf:type mi6:SecretAgent mi6:JamesBond nmm:numberOfGuns “1” MI6 files
68. @arnoutboks #phpce17 RDF Schema vs. JSON/XML Schema Subject Predicate Object mi6:JamesBond rdf:type mi6:SecretAgent mi6:JamesBond nmm:numberOfGuns “1” MI6 files Subject Predicate Object nmm:numberOfGuns rdf:domain nmm:Ship National Maritime Museum (“Scheepvaartmuseum”)
69. @arnoutboks #phpce17 RDF Schema vs. JSON/XML Schema Subject Predicate Object mi6:JamesBond rdf:type mi6:SecretAgent mi6:JamesBond nmm:numberOfGuns “1” nmm:numberOfGuns rdf:domain nmm:Ship mi6:JamesBond rdf:type nmm:Ship
70. @arnoutboks #phpce17 RDF Schema vs. JSON/XML Schema
71. @arnoutboks #phpce17 RDF Schema will never consider data to be invalid
72. @arnoutboks #phpce17 Web Ontology Language (OWL) Even smarter inferencing Web Ontology Language (OWL) Even smarter inferencing
73. @arnoutboks #phpce17 OWL OWL ≈ RDFS++
74. @arnoutboks #phpce17 OWL Power comes at a price…
75. @arnoutboks #phpce17 OWL: Inverse properties Subject Predicate Object :DonaldTrump :isParentOf :IvankaTrump :isParentOf owl:inverseOf :isChildOf :IvankaTrump :isChildOf :DonaldTrump
76. @arnoutboks #phpce17 OWL: Symmetric properties Subject Predicate Object :DonaldTrump :isMarriedTo :MelaniaTrump :isMarriedTo rdf:type owl:SymmetricProperty :MelaniaTrump :isMarriedTo :DonaldTrump
77. @arnoutboks #phpce17 OWL: Equality Subject Predicate Object :DonaldTrump :isMarriedTo :MelaniaTrump :DonaldTrump owl:sameAs :TheDon :TheDon :isMarriedTo :MelaniaTrump
78. @arnoutboks #phpce17 OWL: Functional properties Subject Predicate Object :IvankaTrump :hasFather :DonaldTrump :IvankaTrump :hasFather :TheDon :hasFather rdf:type owl:FunctionalProperty :TheDon owl:sameAs :DonaldTrump
79. @arnoutboks #phpce17 Inconsistency Subject Predicate Object :IvankaTrump :hasFather :DonaldTrump :IvankaTrump :hasFather :TheDon :hasFather rdf:type owl:FunctionalProperty :TheDon owl:differentFrom :DonaldTrump
80. @arnoutboks #phpce17 Inconsistency
81. @arnoutboks #phpce17 Inconsistency
82. @arnoutboks #phpce17 It’s okay to be inconsistent… (remember the AAA slogan)
83. @arnoutboks #phpce17 It’s okay to be inconsistent… (remember the AAA slogan) …but the reasoner won’t help you anymore
84. @arnoutboks #phpce17 Further steps Get going with the Semantic Web
85. @arnoutboks #phpce17 Self-test Subject Predicate Object :George :hasChild :Michelle :George :hasChild :James How many children does George have?
86. @arnoutboks #phpce17 Leveraging the Semantic Web Network effect
87. @arnoutboks #phpce17 Leveraging the Semantic Web Only useful when multiple parties speak the same ‘language’
88. @arnoutboks #phpce17 Align with existing vocabularies
89. @arnoutboks #phpce17 Leveraging the Semantic Web Mapping between vocabularies: • rdfs:subclassOf • rdfs:subpropertyOf • owl:inverseOf • owl:sameAs
90. @arnoutboks #phpce17 Existing vocabularies • Dublin Core • Metadata about publications and authors • Friend of a Friend • People, connections, social networks • GoodRelations • Products, prices, eCommerce • CB-NL • Construction, infrastructure, spatial planning • QUDT • Quantities, units, dimensions, conversions
91. @arnoutboks #phpce17 Resources • Apache Jena • Semantic web framework/tools (written in Java) • easyrdf/easyrdf • RDF parser/writer for PHP • semsol/arc2 • PHP RDF library and MySQL-based triple store • FaCT++, HermiT & Pellet • Open source OWL reasoners • Protégé • RDF/OWL IDE with various reasoner plugins
92. @arnoutboks #phpce17 Resources
93. @arnoutboks #phpce17 Resources • https://www.w3.org/2013/data/ • https://www.w3.org/2001/sw/wiki/ • https://www.w3.org/TR/rdf11-primer/ • https://www.w3.org/TR/owl2-primer/ • https://www.w3.org/TR/sparql11-query/ • http://wiki.dbpedia.org/OnlineAccess • https://www.data.gov/ • http://lod-cloud.net/
94. @arnoutboks #phpce17 Feedback & Questions @arnoutboks @arnoutboks @aboks Arnout Boks Please leave your feedback on joind.in
95. @arnoutboks #phpce17 Image Credits • https://www.flickr.com/photos/lex-photographic/32521124574 • https://www.flickr.com/photos/flamesworddragon/19686463141 • https://www.flickr.com/photos/littlehuw/15236543728 • https://www.flickr.com/photos/crdominguez/422517106 • https://www.flickr.com/photos/pamwood707/5646757752 • https://www.flickr.com/photos/blair25/3240686470 • https://www.flickr.com/photos/tylerbeaulawrence/15167523690 • https://www.flickr.com/photos/23975018@N04/3675503072 • https://www.flickr.com/photos/borkurdotnet/9682277597