Linked Data, Ontologies and Inference
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The document discusses linked data, ontologies, and inference. It provides examples of using RDFS and OWL to infer new facts from schemas and ontologies. Key points include: - Linked Data uses URIs and HTTP to identify things and provide useful information about them via standards like RDF and SPARQL. - Projects like LOD aim to develop best practices for publishing interlinked open datasets. FactForge and LinkedLifeData are examples that contain billions of statements across life science and general knowledge datasets. - RDFS and OWL allow defining schemas and ontologies that enable inferring new facts through reasoning. Rules like rdfs:domain and rdfs:range allow inferring type information
![Class Construction (2)
These class constructs are available in OWL, not in RDFS
The class of female music artists
ObjectIntersectionOf(:Female :MusicArtist)
[a owl:Class;
owl:intersectionOf(:Female :MusicArtist)]
The class of music artists
Female
Music Artist
Solo
≡
EUCLID - Querying Linked Data 39
The class of music artists
ObjectUnionOf(:SoloMusicArtist :MusicGroup)
[a owl:Class;
owl:unionOf(:SoloMusicArtist :MusicGroup)]
Everything that’s not instrumental music
ObjectComplementOf(:InstrumentalMusic)
[a owl:Class;
owl:complementOf(:InstrumentalMusic)]
Solo
Group
Instrumental
≡
≡
NOTE: Anonymous classes!](https://image.slidesharecdn.com/meetupnewyork201304-130511063154-phpapp02/85/Linked-Data-Ontologies-and-Inference-39-320.jpg)
![Naming Class Constructions
• Direct naming can be achieved via owl:equivalentClass
Music Artist
Solo
Group
EquivalentClass(:MusicArtist
ObjectUnionOf(:SoloMusicArtist
:MusicGroup))
≡
EUCLID - Querying Linked Data 40
• This construction provides necessary and sufficient conditions
for class membership
• Class naming can be also achieved using rdfs:subClassOf,
it provides a necessary but insufficient condition for class
membership
Group
:MusicArtist owl:equivalentClass
[owl:unionOf (:SoloMusicArtist :MusicGroup)]](https://image.slidesharecdn.com/meetupnewyork201304-130511063154-phpapp02/85/Linked-Data-Ontologies-and-Inference-40-320.jpg)
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Linked Data, Ontologies and Inference
- 1. Barry Norton, Solutions Architect Ontotext (UK), London SemWeb Meet-up, NYC, April 2013 Linked Data, Ontologies and Inference
- 2. Linked Data • Defined in a W3C Technical Note including these core principles: 1. Use URIs as names for things 2. Use HTTP URIs so that people can look up those2. Use HTTP URIs so that people can look up those names. 3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL) 4. Include links to other URIs. so that they can discover more things. 2
- 3. Linked Open Data • The Linking Open Data (LOD) project of the W3C Semantic Web Outreach and Education Task Force has developed adeveloped a good deal of best practice and exposed a large number of interlinked datasets 3
- 4. • Many datasets – variety of publishers • Re-using URIs enables Linked Data • Browse using URIs to datasets Linked DataVision #4
- 5. FactForge and LinkedLifeData Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/ #5
- 6. • FactForge (indicated in red on the next slide) – Some of the central LOD datasets – General-knowledge information – 1.2B explicit plus .9B inferred indexed, 10B retrievable statements – http://www.factforge.net/ FactForge: Contents • Linked Life Data (indicated in yellow) – 25 of the most popular life-science datasets – Complemented by gluing ontologies – 2.7B explicit and 1.4B inferred, total of 4.1B indexed statements – http://www.linkedlifedata.com #6
- 7. • Datasets: DBPedia, Freebase, Geonames, UMBEL, MusicBrainz, Wordnet, CIA World Factbook, Lingvoj • Ontologies: Dublin Core, SKOS, RSS, FOAF • Inference: materialization with respect to OWL2 RL – owl:sameAs optimization in BigOWLIM allows reduction of the indices without loss of semantics, but big gains in performance FactForge indices without loss of semantics, but big gains in performance • Free public service at http://www.factforge.net, – Incremental URI auto-suggest – Query and explore through Forest and Tabulator – RDF Search: retrieve ranked list of URIs by keywords – SPARQL end-point #7
- 8. Dataset Explicit Indexed Triples ('000) Inferred Indexed Triples ('000) Total # of Stored Triples ('000) Entities ('000 of nodes in the graph) Inferred closure ratio Sechmata and ontologies 11 7 18 6 0.6 DBpedia (categories) 2,877 42,587 45,464 1,144 14.8 DBpedia (sameAs) 5,544 566 6,110 8,464 0.1 UMBEL 5,162 42,212 47,374 500 8.2 FactForge: Datasets UMBEL 5,162 42,212 47,374 500 8.2 Lingvoj 20 863 883 18 43.8 CIA Factbook 76 4 80 25 0.1 Wordnet 2,281 9,296 11,577 830 4.1 Geonames 91,908 125,025 216,933 33,382 1.4 DBpedia core 560,096 198,043 758,139 127,931 0.4 Freebase 463,689 40,840 504,529 94,810 0.1 MusicBrainz 45,536 421,093 466,630 15,595 9.2 Total 1,177,961 881,224 2,058,185 283,253 0.7 #8
- 9. Querying Linked Data Presented by: Barry Norton
- 10. Motivation: Music! Visualization Module Application Analysis & Mining Module LDDatasetAccess Vocabulary SPARQL Endpoint Publishing RDFa 10 Metadata Streaming providers Physical Wrapper Downloads Dataacquisition D2R Transf.LD Wrapper Musical Content LDDataset LD Wrapper RDF/ XML Integrated Dataset Interlinking Cleansing Vocabulary Mapping Other content
- 11. • The data of interest may be stored in a wide range or formats: Extracting the Data • Several tools support the process of mining data from different repositories, for example: 11EUCLID - Providing Linked Data Spreadsheets or tabular data Databases Text R2RML
- 12. Reasoning for Linked Data Integration • Example: Integration of the MusicBrainz data set and the DBpedia data set Integration EUCLID - Querying Linked Data 12 Integration Data set Data set
- 13. Reasoning for Linked Data Integration mo:b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d foaf:name The Beatles; mo:member mo:ba550d0e-adac-4864-b88b-407cab5e76af; mo:member mo:4d5447d7-c61c-4120-ba1b-d7f471d385b9; mo:member mo:42a8f507-8412-4611-854f-926571049fa0; dbpedia:The_Beatles dbpedia-ont:origin dbpedia:Liverpool; dbpedia-ont:genre dbpedia:Rock_music; foaf:depiction . same EUCLID - Querying Linked Data 13 mo:42a8f507-8412-4611-854f-926571049fa0; mo:member mo:300c4c73-33ac-4255-9d57-4e32627f5e13. Integration Data set Data set
- 14. Reasoning for Linked Data Integration mo:b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d foaf:name The Beatles; mo:member mo:ba550d0e-adac-4864-b88b-407cab5e76af; mo:member mo:4d5447d7-c61c-4120-ba1b-d7f471d385b9; mo:member mo:42a8f507-8412-4611-854f-926571049fa0; dbpedia:The_Beatles dbpedia-ont:origin dbpedia:Liverpool; dbpedia-ont:genre dbpedia:Rock_music; foaf:depiction . same EUCLID - Querying Linked Data 14 mo:42a8f507-8412-4611-854f-926571049fa0; mo:member mo:300c4c73-33ac-4255-9d57-4e32627f5e13. SELECT ?m ?g WHERE { dbpedia:The_Beatles dbpedia-ont:genre ?g; mo:member ?m.} Query: ?m ?g mo:ba550d0e-adac-4864-b88b- 407cab5e76af dbpedia:Rock_music mo:4d5447d7-c61c-4120-ba1b- d7f471d385b9 dbpedia:Rock_music mo42a8f507-8412-4611-854f- 926571049fa0; dbpedia:Rock_music mo300c4c73-33ac-4255-9d57- 4e32627f5e13 dbpedia:Rock_music Result set:
- 15. SPARQL 1.1: Entailment Regimes • SPARQL 1.0 was defined only for simple entailment (pattern matching ) • SPARQL 1.1 is extended with entailment regimes other than simple entailment: – RDF entailment EUCLID - Querying Linked Data 15 – RDF entailment – RDFS entailment – D-Entailment – OWL RL entailment – OWL Full entailment – OWL 2 DL, EL, and QL entailment – RIF entailment Source: http://www.w3.org/TR/rdf-mt/#RDFSRules
- 16. RDFS Resource Description Framework Schema Taxonomies and inferences EUCLID - Querying Linked Data 16 Semantic Web Stack Berners-Lee (2006) Taxonomies and inferences
- 17. RDFS Entailment Regimes • Contains 13 entailment rules denominated rdfsi for inference over RDFS definitions*: – rdfs:Literal (rdfs1, rdfs13) – rdfs:domain (rdfs2), rdfs:range (rdfs3) – rdfs:Resource (rdfs4a, rdfs4, rdfs8) EUCLID - Querying Linked Data 17 – rdfs:Resource (rdfs4a, rdfs4, rdfs8) – rdfs:subPropertyOf (rdfs5, rdfs6, rdfs7, rdfs12) – rdfs:Class (rdfs8, rdfs10) – rdfs:subClassOf (rdfs9, rdfs10, rdfs11) – rdfs:ContainerMembershipProperty (rdfs12) – rdfs:Datatype (rdfs13) * Source: http://www.w3.org/TR/rdf-mt/#RDFSRules
- 18. rdfs2 – rdfs:domain dbpedia: The_Beatles dbpedia: Paul_McCartney mo:member Schema: Query: dbpedia: John_Lennon dbpedia: George_Harrison dbpedia: Ringo_Starr mo:member mo:member mo:member EUCLID - Querying Linked Data 18 SELECT ?x WHERE { ?x a mo:MusicGroup.} mo:member rdfs:domain mo:MusicGroup . ?x ?x dbpedia:The_Beatles … Schema: Query: Result set: Result set with inference:
- 19. rdfs3 – rdfs:range dbpedia: The_Beatles dbpedia: Paul_McCartney dbpedia-ont: bandMember Schema: Query: dbpedia: John_Lennon dbpedia: George_Harrison dbpedia: Ringo_Starr dbpedia-ont: bandMember dbpedia-ont: bandMember dbpedia-ont: bandMember EUCLID - Querying Linked Data 19 SELECT ?x WHERE { ?x a foaf:Agent.} mo:member rdfs:range foaf:Agent . ?x ?x dbpedia:Paul_McCartney dbpedia:John_Lennon dbpedia:Ringo_Starr dbpedia:George_Harrison … Schema: Query: Result set: Result set with inference:
- 20. rdfs7 – rdfs:subPropertyOf dbpedia: Yesterday dbpedia: Paul_McCartney mo:singer Schema: Query: dbpedia: John_Lennon dbpedia: George_Harrison dbpedia: Ringo_Starr mo:performer mo:performermo:performer mo:performer EUCLID - Querying Linked Data 20 SELECT ?x WHERE { dbpedia:Yesterday mo:performer ?x.} mo:singer rdfs:subPropertyOf mo:performer . ?x dbpedia:John_Lennon dbpedia:Ringo_Starr dbpedia:George_Harrison ?x dbpedia:John_Lennon dbpedia:Ringo_Starr dbpedia:George_Harrison dbpedia:Paul_McCartney Schema: Query: Result set: Result set with inference:
- 21. rdfs9 – rdfs:subClassOf dbpedia: The_Beatles Schema: Query: mo: MusicArtist rdf:type mo: MusicGroup rdf:type EUCLID - Querying Linked Data 21 SELECT ?x WHERE { ?x a mo:MusicArtist.} mo:MusicGroup rdfs:subClassOf mo:MusicArtist . ?x ?x dbpedia:The_Beatles … Schema: Query: Result set: Result set with inference:
- 22. Inference from Schema • Knowledge encoded in the schema leads to infer new facts mo:MusicGroup rdfs:subClassOf mo:MusicArtist . mo:MusicGroup a rdfs:Class . mo:MusicArtist a rdfs:Class . Schema: Inferred facts: EUCLID - Querying Linked Data 22 • This is also captured in the set of axiomatic triples, which provide basic meaning for all the vocabulary terms mo:MusicArtist a rdfs:Class .facts: rdfs:subClassOf rdfs:domain rdfs:Class . rdfs:subClassOf rdfs:range rdfs:Class .
- 23. RDFS: Lack of Consistency Check • It is possible to infer facts that seem incorrect facts, but RDFS cannot prevent this: Schema: mo:member rdfs:domain mo:MusicGroup ; rdfs:range foaf:Agent . EUCLID - Querying Linked Data 23 Existing :PaulMcCartney a :SoloMusicArtist ; facts: :member :TheBeatles . Inferred :PaulMcCartney a :MusicGroup . facts: No contradiction!: The mis-modeling is not diagnosed rdfs2
- 24. • We might wish further inferences, but these are beyond the entailment rules implemented by RDFS RDFS: Inference Limitations foaf:knows rdfs:domain foaf:Person ; rdfs:range foaf:Person . foaf:made rdfs:domain foaf:Agent . :PaulMcCartney foaf:made :Yesterday ; Schema: Existing EUCLID - Querying Linked Data 24 :PaulMcCartney foaf:made :Yesterday ; foaf:knows :RingoStarr . :PaulMcCartney a foaf:Agent ; a foaf:Person . :RingoStarr a foaf:Person . Existing fact: Inferred facts: :Yesterday dc:creator :PaulMcCartney. :RingoStarr foaf:knows :PaulMcCartney . These inferences require OWL! NOT inferred: Cannot model with RDFS that ‘x knows y’ implies ‘y knows x’ Cannot model with RDFS that if ‘x makes y’ implies that ‘the creator of y is x’
- 25. OWL Web Ontology Language Ontologies and inferences EUCLID - Querying Linked Data 25 Semantic Web Stack Berners-Lee (2006) Ontologies and inferences
- 26. Introduction to OWL • Provides more ontological constructs and avoids some of the potential confusion in RDFS • OWL 2 is divided into sub-languages denominated profiles: – OWL 2 EL: Limited to basic classification, but with polynomial-time reasoning EUCLID - Querying Linked Data 26 but with polynomial-time reasoning – OWL 2 QL: Designed to be translatable to relational database querying – OWL 2 RL: Designed to be efficiently implementable in rule-based systems • Most triple stores concentrate on the use of RDFS with a subset of OWL features, called OWL-Horst or RDFS++ More restrictive than OWL DL
- 27. OWL Properties OWL distinguishes between two types of properties: • OWL ObjectProperties: resources as values • OWL DatatypeProperties: literals as values :plays rdf:type owl:ObjectProperty; EUCLID - Querying Linked Data 27 :plays rdf:type owl:ObjectProperty; rdfs:domain :Musician; rdfs:range :Instrument . :hasMembers rdf:type owl:DatatypeProperty; rdfs:domain :MusicGroup rdfs:range xsd:int .
- 28. PropertyAxioms • Property axioms include those from RDF Schema • OWL allows for property equivalence. Example: EquivalentObjectProperties(dbpedia-ont:bandMember mo:member) dbpedia-ont:bandMember owl:equivalentProperty mo:member. ≡ Query: EUCLID - Querying Linked Data 28 dbpedia: The_Beatles dbpedia: Paul_McCartney mo:member dbpedia: John_Lennon dbpedia: George_Harrison dbpedia: Ringo_Starr mo:member mo:member mo:member SELECT ?x {dbpedia:The_Beatles dbpedia-ont:bandMember ?x.} Query: ?x Result set: ?x dbpedia:Paul_McCartney dbpedia:John_Lennon dbpedia:Ringo_Starr dbpedia:George_Harrison Result set with inference:
- 29. PropertyAxioms • Property axioms include those from RDF Schema • OWL allows for property equivalence. Example: EquivalentObjectProperties(dbpedia-ont:bandMember mo:member) dbpedia-ont:bandMember owl:equivalentProperty mo:member. ≡ EUCLID - Querying Linked Data 29 • OWL allows for property disjointness. Example: DisjointObjectProperty(dbpedia-ont:length mo:duration) dbpedia-ont:length owl:propertyDisjointWith mo:duration. • There is no standard for implementing inconsistency reports under SPARQL ≡
- 30. PropertyAxioms (2) OWL allows the definition of property characteristics to infer new facts relating to instances and their properties • Symmetry • Transitivity EUCLID - Querying Linked Data 30 • Transitivity • Inverse • Functional • Inverse Functional
- 31. Property Axioms: Symmetry dbpedia: The_Beatles dbpedia: Plastic_Ono_ Band :associatedMusicalArtist a owl:SymmetricProperty .:associatedMusicalArtist Schema: SELECT ?x WHERE { dbpedia:The_Beatles Query: :associatedMusicalArtist EUCLID - Querying Linked Data 31 dbpedia: Billy_Preston ?genre dbpedia:Plastic_Ono_Band ?genre dbpedia:Plastic_Ono_Band dbpedia:Billy_Preston Result set: Result set with inference: dbpedia:The_Beatles :associatedMusicalArtist ?x.} :associatedMusicalArtist
- 32. Property Axioms: Transitivity :Rock :Heavy_:Heavy_ metal :Punk_:Punk_ rock SELECT ?genre WHERE { :Rock :subgenre ?genre .} :subgenre a owl:TransitiveProperty .:subgenre :subgenre :subgenre :subgenre Schema: Query: EUCLID - Querying Linked Data 32 :Black_:Black_ metal :Rock :subgenre ?genre .} ?genre :Heavy_metal :Punk_rock ?genre :Heavy_metal :Punk_rock :Black_metal Result set: Result set with inference:
- 33. Property Axioms: Inverse SELECT ?x WHERE { ?x mo:member_of mo:member_of owl:inverseOf mo:member. Schema: Query: dbpedia: The_Beatles mo:member_of dbpedia: John_Lennon dbpedia: George_Harrison mo:member mo:member_of mo:member mo:member_of mo:member_of EUCLID - Querying Linked Data 33 ?x mo:member_of dbpedia:The_Beatles .} ?x dbpedia:John_Lennon dbpedia:George_Harrison ?x dbpedia:John_Lennon dbpedia:George_Harrison dbpedia:Paul_McCartney dbpedia:Ringo_Starr Result set: Result set with inference: dbpedia: Paul_McCartney dbpedia: Ringo_Starr mo:member_of mo:member_of
- 34. Example: Every artist primarily plays only one musical instrument Property Axioms: Functional It refers to a property that can have only one (unique) value for each instance r2 same r1 mo:primary_instrument rdf:type owl:FunctionalProperty . dbpedia:Jimi_Hendrix mo:primary_instrument dbpedia:Electric_Guitar. dbpedia:Jimi_Hendrix mo:primary_instrument dbpedia:E-Guitar. Conclusion dbpedia:Electric_Guitar owl:sameAs dbpedia:E-Guitar . EUCLID - Querying Linked Data 34 r2 same
- 35. Example: Every recording has a unique ISRC (International Standard Recording Code) Property Axioms: Inverse Functional It is useful for specifying unique properties identifying an individual r2 same r1 mo:isrc rdf:type owl:InverseFunctionalProperty . mo:21047249-7b3f-4651-acca-246669c081fd mo:isrc "GBAYE6300412" . dbpedia:She_Loves_You mo:isrc "GBAYE6300412" . Conclusion mo:21047249-7b3f-4651-acca-246669c081fd owl:sameAs :dbpedia:She_Loves_You . EUCLID - Querying Linked Data 35 r2 same
- 36. Individual Axioms OWL Individuals represent instances of classes. They are related to their class by the rdf:type property • We can state that two individuals are the same SameIndividual(<artist/ba550d0e-adac-4864-b88b-407cab5e76af#_> dbpedia:PaulMcCartney) <artist/ba550d0e-adac-4864-b88b-407cab5e76af#_> owl:sameAs dbpedia:PaulMcCartney . ≡ EUCLID - Querying Linked Data 36 <artist/ba550d0e-adac-4864-b88b-407cab5e76af#_> owl:sameAs dbpedia:PaulMcCartney . • We can state that two individuals are different DifferentIndividuals(:TheBeatles_band :TheBeatles_TVseries) :TheBeatles_band owl:differentFrom :TheBeatles_Tvseries . ≡ ≡
- 37. Class Axioms Axioms declare general statements about concepts which are used in logical inference (reasoning). Class axioms: • Sub-class relationship (from RDF Schema) • Equivalent relationship: classes have the same individuals EquivalentClass(:Musician :MusicArtist) EUCLID - Querying Linked Data 37 EquivalentClass(:Musician :MusicArtist) :Musician owl:equivalentClass :MusicArtist . • Disjointness: classes have no shared individuals DisjointClasses(:SoloMusicArtist :MusicGroup) :SoloMusicArtist owl:disjointWith :MusicGroup . ≡ ≡
- 38. Class Construction • OWL classes are defined by the OWL term owl:Class • OWL classes can be subclassed as in RDFS: EUCLID - Querying Linked Data 38 • OWL classes may be combined with class constructs to build new classes Music Artist Artist :MusicArtist rdfs:subClassOf :Artist .
- 39. Class Construction (2) These class constructs are available in OWL, not in RDFS The class of female music artists ObjectIntersectionOf(:Female :MusicArtist) [a owl:Class; owl:intersectionOf(:Female :MusicArtist)] The class of music artists Female Music Artist Solo ≡ EUCLID - Querying Linked Data 39 The class of music artists ObjectUnionOf(:SoloMusicArtist :MusicGroup) [a owl:Class; owl:unionOf(:SoloMusicArtist :MusicGroup)] Everything that’s not instrumental music ObjectComplementOf(:InstrumentalMusic) [a owl:Class; owl:complementOf(:InstrumentalMusic)] Solo Group Instrumental ≡ ≡ NOTE: Anonymous classes!
- 40. Naming Class Constructions • Direct naming can be achieved via owl:equivalentClass Music Artist Solo Group EquivalentClass(:MusicArtist ObjectUnionOf(:SoloMusicArtist :MusicGroup)) ≡ EUCLID - Querying Linked Data 40 • This construction provides necessary and sufficient conditions for class membership • Class naming can be also achieved using rdfs:subClassOf, it provides a necessary but insufficient condition for class membership Group :MusicArtist owl:equivalentClass [owl:unionOf (:SoloMusicArtist :MusicGroup)]
- 41. For exercises, quiz and further material visit our website: http://www.euclid-project.eu eBook Course EUCLID - Providing Linked Data 41 @euclid_project EUCLID project EUCLIDproject Other channels: