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Wissenstechnologie Iv 08 09


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  • 1. Wissenstechnologie WS 08/09 Michael Granitzer IWM TU Graz & Know-Center Know Center Lecture 4: OWL Inference Lect e 4 OWL, Infe ence and Upper Ontologies http://kmi tugraz at http://www know center at This work is licensed under the Creative Commons Attribution 2.0 Austria License. To view a copy of this license, visit
  • 2. Today RDF Schema (RDFS) Web Ontology Language (OWL) OWL & Logics Example Ontologies 2 WS 08/09 Wissenstechnologie @
  • 3. Semantic Web Stack a.k.a. SW Layer Cake y a.k.a. SW Tower 3 WS 08/09 Wissenstechnologie @
  • 4. Semantic Web Stack RDF 4 WS 08/09 Wissenstechnologie @
  • 5. RDF Statements (Triples) A small example htt // iki di / iki/J h L http://dbpedia org/property/associatedActs rdfs:label „Paul McCartney“ Subject j Predicate Object j ohn_Lennon ssociatedActs he_Beatles aul_McCartney ssociatedActs he_Beatles Rdfs:label “Paul McCartney” 5 aul_McCartney WS 08/09 Wissenstechnologie @
  • 6. Ontologies What are Concepts in our purpose? Semiotic Triangle [Ogden & Richards 1923] Concept Refers to Symbolizes Term / Word Thing /URI Stands for St d f ‚Apache‘ 6 WS 08/09 Wissenstechnologie @
  • 7. Ontologies & Semantics Example: Mammal Intension •isA(Vertebrate Animal) •has(Sweat glands) •withFunction(Milk) •withFunction(hair) •.... Extension •Elephant •Lion •Monkey Monkey •.... 7 WS 08/09 Wissenstechnologie @
  • 8. Summary of Definitions A Ontology is a model (of the world) t l A ontology d ib describes a particular (k ti l (knowledge) d l d ) domain i A ontologie defines words/terms/signs for describing Concepts A ontologie puts concepts into relation to each other A ontologie uses axioms to put constraints on particular concepts 8 WS 08/09 Wissenstechnologie @
  • 9. Components of an Ontology Classes general things of a domain Instances special things of a domain R l ti Relations between thi b t things Properties of things 9 WS 08/09 Wissenstechnologie @
  • 10. Semantics & Communication Language must allow to express the semantics in an implementation/algorithmic independent way Usually done via a Vocabulary Topic oriented vocabulary (e.g. Friend of a friend) Schema Knowledge/Terminological Knowledge g g g – Special vocabulary to make statements over topic oriented vocabulary (i.e. the termonologie used in a domain) – A general set of rules independent of the domain – Defines the expressiveness of a language 10 WS 08/09 Wissenstechnologie @
  • 11. Semantic Web Stack RDF Schema 11 WS 08/09 Wissenstechnologie @
  • 12. RDF Schema (RDFS) http://www w3 org/2000/01/rdf-schema# Allows to express terminological knowledge over RDF Application of RDFS Defines a new vocabulary for giving meaning independent of program logic Allows to define „lightweight“ Ontologies and basic g g g Reasoning capabilities 12 WS 08/09 Wissenstechnologie @
  • 13. RDF Schema Classes rdfs:Resource Class of all resources rdfs:Literal Class of literals (Strings) rdfs:Class Class of classes rdf:Property Class of properties rdf:Statement Class of RDF Statements … 13 WS 08/09 Wissenstechnologie @
  • 14. RDF Schema Properties rdf:type Subject is an instance of a class rdfs:subClassOf Subject is a subclass of a class rdfs:subPropertyOf Subject is a sub property of a property rdfs:domain A possible class for a subject of a property rdfs:range A possible class for an object of a property rdfs:label human readable label of an resource rdfs:comment human readable comment of an resource … 14 WS 08/09 Wissenstechnologie @
  • 15. RDFS Semantics Model based semantics: each triple is a sentence A sentence is tr true, if the triple exists Entailment: Given a graph the graph is transformed according to the rules of RDFS Implicit knowledge (i e not explicitly modelled) (i.e. #Means of #Means of Transportation Transportation rdfs:subClassOf rdf:type rdfs:subClassOf #MyBMW #Car #MyBMW #Car rdf:type rdfs:subClassOf rdf:type 15 rdfs:subClassOf #BMW #BMW WS 08/09 Wissenstechnologie @
  • 16. RDFS Semantics Drawback/Restriction of RDF Open world assumption: false statements must be specified Closed world assumption: if a statement is missing, it is p g, assumed to be false No negation in RDFS possible • ex:michael rdf:type ex:nonsmoker • ex:michael rdf:type ex:smoker Does not lead to a contradiction! No l N rules over individuals e.g. ex:Humans = All i di id l H ex:Women and All ex:Men 16 No Counting: “An Elephant has 4 legs” An legs WS 08/09 Wissenstechnologie @
  • 17. Semantic Web Stack Web Ontology Language (OWL) OWL 17 WS 08/09 Wissenstechnologie @
  • 18. Historical Development Standardised since 2004 18 WS 08/09 Wissenstechnologie @
  • 19. DARPA Agent Markup Language (DAML) DARPA, Funded by DARPA start 2001 DARPA: Defense Advanced Research Projects Agency j g y Markup Language for semantic nets DAML-ONT: DAML ONT: RDFS extension for Ontologies Focus is on the Web 19 WS 08/09 Wissenstechnologie @
  • 20. Ontology Inference Layer (OIL) European Project with focus on inference capabilities Different kinds of standard Excluding Reification Core OIL is compatible to RDFS 20 WS 08/09 Wissenstechnologie @
  • 21. History DAML+OIL 1999 DARPA Agent Markup Language (DAML) in USA Ontology Inference Layer (OIL) in EU 2000 Combining both DAML+OIL 2001 DAML+OIL handed in to W3C for standardisastion Base for Web Ontology Language (OWL) 21 WS 08/09 Wissenstechnologie @
  • 22. Development of OWL W3C founded 2001 The Ontology (WebONT) Working Group Using DAML+OIL for language specification g g g p Feb. 2004 the W3C has published the OWL Web Ontology Language Recommendations Simply speaking: They added an additional vocabulary to RDF(S) htt // 3 /2001/ /W bO t 22 WS 08/09 Wissenstechnologie @
  • 23. OWL - WOL Web Language The language started out as the quot;Web Ontology Languagequot; but the Working Group disliked the acronym quot;WOL.quot; We decided to call it OWL. The Working Group became more comfortable with this decision when one of the members pointed out the following justification for this decision from the noted ontologist A.A. Milne who, in his influential book quot;Wi i th P hquot; stated of th wise character OWL quot;Winnie the Poohquot; t t d f the i h t OWL: quot;He could spell his own name WOL, and he could spell Tuesday so that you knew it wasn't Wednesday quot; wasn t Wednesday... 23 WS 08/09 Wissenstechnologie @
  • 24. OWL - WOL Owl Winnie the Pooh Piglet 24 WS 08/09 Wissenstechnologie @
  • 25. OWL The second story y Jim Hendler wrote: > ... Dieter is right about that as well) I prefer the three letter WOL to the longer SWOL. How about OWL as a variation. The words would be the same (Ontology Web Language) but it has several advantages: (1) it has just one obvious pronunciation which is easy on the ear; (2) it opens up great i ti hi h i th t opportunities for logos; (3) owls are associated with wisdom; (4) it has an interesting back story. OWL has probably been used for many computer languages and projects (see below), but I don't think that is a show stopper. • But the Background is: quot;One World Language“ short OWL in the mid 70‘s developed at MIT 25 WS 08/09 Wissenstechnologie @
  • 26. OWL - Specifications OWL besteht aus 3 Untersprachen OWL Lite OWL DL OWL Full 26 WS 08/09 Wissenstechnologie @
  • 27. OWL - Specification The following set of relations hold. Their inverses do not: Every legal OWL Lite ontology i a legal OWL DL ontology. is l l t l Every legal OWL DL ontology is a legal OWL Full ontology ontology. Every valid OWL Lite conclusion is a valid OWL DL conclusion. Every valid OWL DL conclusion is a valid OWL Full conclusion. 27 WS 08/09 Wissenstechnologie @
  • 28. OWL Syntax and Semantic Namespace & Header In addition to rdfs and rdf: <rdf:RDF … xmlns:owl = „“> <owl:Ontology rdf:about=„“> <rdfs:comment>my best ontology</rdfs:comment> <owl:versinoInfo>v0.5</owl:verisonInfo> …. </owl:Ontology> Combines Elements of OWL and RFDS Namespace Import of other ontologies possible <owl:imports rdf:resource=uri> 28 WS 08/09 Wissenstechnologie @
  • 29. OWL Syntax and Semantic Classes, Classes Individuals and Roles (i.e. Classes similar to RDFS (i e subclass of rdfs:Class) owl:Class Individuals are similar to instances in RDFS Definition via the property rdf:type <rdf:Description rdf:about=„KlausTochtermann“> f p f „ <rdf:type rdf:resource=„Professor“/> </rdf:Description> Abbrevated Notation in XML: <Class rdf:about=URI> <Professor rdf:about=„KlausTochtermann“/> 29 WS 08/09 Wissenstechnologie @
  • 30. OWL Syntax and Semantic Roles (properties in RDF) owl:DataTypeProperty (rdf:Domain ~ rdf:Literal|rdf:DataType|xsd:xxx) <owl:DatatypeProperty rdf:about=„Name“> <rdfs:domain rdf:resource=„Professor“/> <rdfs:range rdf:resource= xsd:String“/> rdf:resource=„xsd:String“/> </owl:DatatypeProperty> owl:ObjectProperty ( df D l Obj tP t (rdf:Domain ~ owl:Thing) i l Thi ) <owl:ObjectProperty rdf:about=„lecturing“> <rdfs:domain rdf:resource=„Professor“/> <rdfs:range rdf:resource=„Lecture“/> </owl:ObjectProperty> owl:annotationProperty Just for commenting on resources 30 WS 08/09 Wissenstechnologie @
  • 31. OWL Syntax and Semantic Simple Properties between Classes rdfs:subClassOf Similar to RDFS All classes are sublcasses from owl:Thing All classes have the sub class owl:Nothing owl:disjointWith No individual is contained in both classes <owlClass rdf:about=„Human“/> / <owlClass rdf:about=„Animal“> <owl:disjointWith rdf:resource=„Human“/> </owlClass> owl:equivalentClass Two classes are semantically equal 31 WS 08/09 Wissenstechnologie @
  • 32. OWL Syntax and Semantic Properties between Individuals Owl:sameAs two individuals are the same <Professor rdf:about=„KlausTochtermann“/> <owl:sameAs rdf:resource=„ProfessorTochtermann“> </Professor> owl:differentFrom two individuals are different owl:AllDifferent Abrevation for a set of individuals owl:distinctMembers <owl:AllDifferent> <owl:distinctMembers rdf:parseType=„Collection“> <Person rdf:about=„MichaelGranitzer“> <Person rdf:about=„MarkusStrohmaier“> <Person rdf:about KlausTochtermann“> rdf:about=„KlausTochtermann“> </olw:distinctMembers> 32 </owl:AllDifferent> WS 08/09 Wissenstechnologie @
  • 33. OWL Syntax and Semantic Properties between Individuals owl:oneOf classes, i.e. closed classes i e class with a fixed number of members <owl:Class rdf:about=„IWMLecturers“> <owl:oneOf rdf:parseType=„Collection“> <Person rdf:about=„MichaelGranitzer“> <Person rdf:about=„MarkusStrohmaier“> <Person rdf:about=„KlausTochtermann“> rdf:about „KlausTochtermann > </olw:oneOf> </owl:Class> 33 WS 08/09 Wissenstechnologie @
  • 34. OWL Syntax and Semantic Logical Constructors for Classes Logical construtors on „simple classes allow to construct new simple“ complex classes Human =Women U Men owl:unionOf <owl:Class rdf:about=„Women“/> logical OR <owl:Class rdf:about=„Men“> <owl:complementOf rdf:resource=„Women“> owl:complementOf </owl:Class> logical Not <owl:Class rdf:about=„Human“/> <owl:unionOf rdf:parseType=„Collection“> owl:intersectionOf <owl:Class rdf:about=„Men“> <owl:Class rdf:about=„Women“> logical AND </owl:unionOf> </owl:Class> 34 WS 08/09 Wissenstechnologie @
  • 35. OWL Syntax and Semantic Logical Constructors for Classes Complex class construtors via role restrictions Defines a class as set of object for which the role has a value of a specific class owl:someValuesFrom owl:allValuesFrom Owl:hasValue Cardinality of roles owl:maxCardinaltiy owl:minCardinality owl:cardinality 35 WS 08/09 Wissenstechnologie @
  • 36. OWL Syntax and Semantic Relationships between Roles/Role Properties Relationships between roles owl:subPropertyOf Hierarchy for properties owl:inverseOf inverse role Properties of roles Symmetry role(A,B) = role(B,A) <MichaelGranitzer, worksTogetherWith,MarkusStrohmaier> Transitivity role(A,B) && role(B,C) role (A,C) <Transistor, isPartOf, Chip> && <Chip, isPartOf,Laptop> <Transisotr,isPartOf,Laptop> Functional role(A,B) && role (A,C) <B,sameAs,A> <MichaelGranitzer, isLecturerOf, Wissenstechnologie> <GranitzerMichael, isLecturerOf, Wissenstechnologie> Inverse Functional role(B,A) && role (C,A) <B,sameAs,A> 36 WS 08/09 Wissenstechnologie @
  • 37. OWL Syntax and Semantic semantics-20040210/ 37 WS 08/09 Wissenstechnologie @
  • 38. OWL Full Highest possible expressiveness using OWL Constraint: Must be valid RDF D id bilit i not guaranteed Decidability is t t d No distinction between roles, classes and instances An instance may be a class of another instance (Meta- modelling) – <Car rdf:about=„BMW“> <BMW rdf:about=„MyBMW“> 38 WS 08/09 Wissenstechnologie @
  • 39. OWL DL p g DL….Description Logics Guranteed to be deciable Contains all elements of OWL but only some elements of RDFS (mainly rdfs:class and rdf:Property) Separation of classes, roles and instances Restrictions on specific roles for classes and instances Completeness (all implications can be calcualted) Decidability (all calcualtions can be done in finite time) With maximum expressiveness 39 WS 08/09 Wissenstechnologie @
  • 40. OWL Lite Simplest form of OWL Restriction on class constructors R t i ti di lit Restrictions on cardinality Predefined class names and role restrictions in specific situations Hardly used in practice 40 WS 08/09 Wissenstechnologie @
  • 41. Editors for OWL Protégé: Altova SemanticWorks (comercial): ( ) SWOOP: htt // i d /2004/SWOOP/ TopBraid Composer™ (comercial): http://www topbraidcomposer com/ 41 WS 08/09 Wissenstechnologie @
  • 42. OWL Inference and Reasoning OWL DL uses Description Logics (Beschreibungslogik) DL is a subset of First Order B Benefits f fit from L i Logic Well known Logic, studied over years Known runtime complexibility Existing algorithms for reasoning 42 WS 08/09 Wissenstechnologie @
  • 43. OWL Inference and Reasoning Important Properties Expressive Power (Aussdrucksstärke) What statements can be made over the model? C Computability (B t bilit (Berechenbarkeit) h b k it) Can the evaluation algorithm be calculated in finite time? Decideability (Entscheidbarkeit) Given a logical systems, is there an computable algorithm to evaluate a given formula? (e.g. decide whether it is true or false) ) Tradeoff: Expressive Power vs. Decideability 43 Open vs Closed World Assumption vs. WS 08/09 Wissenstechnologie @
  • 44. Logic Families Propositonal Logic ( warm ∨ hot ) → cowFeelsWell Predicate Logic: Formulas contain variables and quantifiers First Order Logic – D Description L i i ti Logic Second Order Logic Many-sorted logic … Temporal Logic 44 WS 08/09 Wissenstechnologie @
  • 45. Propositonal Logic Elements El Atoms: P, Q, R, … Constants: T C t t True, F l False Junctors: ∧,∨, ¬, →, ↔ Klammern: (, ) ( Example ( warm ∨ hot ) → cowFeelsWell 45 WS 08/09 Wissenstechnologie @
  • 46. First Order Logic Elemente Constants: a, b, John, Animal, Mammal … Variables: x, y, z, … , , Extension to Functions: f, g, Mapping from constants to constants propositional Logic like Predicate: P(x), Q(y), P di t P( ) Q( ) Mapping von variables to constants ( warm ∨ hot ) → cowFeelsWell Quantoren: ∀ , ∃ Brackets: (, ) Example (∀x)isCow( x) → isCow(mother ( x)) 46 WS 08/09 Wissenstechnologie @
  • 47. Description Logics Knowledge representation via Classes I di id l Individuals Roles (Properties) Subset of First Order Logic Family having different languages depending on the expressiveness 47 WS 08/09 Wissenstechnologie @
  • 48. Description Logic TBox (terminological box) Statements over concepts Class models and class roles ABox (assertional box) Statements over Individuals Assignment of Individuals to classes and filling the roles OWL DL: TBox and ABox are disjunct OWL-DL: E.g. no Class can be an individual E.g. E g no roles can be individuals 48 WS 08/09 Wissenstechnologie @
  • 49. Description Logics Family Member ALC ALC – Attributive Language with Complement Class, Role and Individual A i Assignment of I di id l t classes t f Individuals to l Equivalence, disjunction and conjunction of classes owl:Thing, owl:Nothing owl:intersectionOF, owl:complementOf owl:allValuesFrom, owl:somealuesFrom rdfs:range, rdfs:range rdfs:domain 49 WS 08/09 Wissenstechnologie @
  • 50. Description Logics Family Member SHOIN(D) SHOIN OWL DL SHOIN– Standard OWL-DL Logic S: ALC including transitivity of roles H: b t df H sub property, rdfs:subPropertyOf bP t Of O: owl:oneOf (closed classes) I: owl:inverseOf (inverse roles) N: Restrictions on numbers D: Allows datatypes (owl:DataType) 50 WS 08/09 Wissenstechnologie @
  • 51. Description Logics Family Member SHIF(D) SHIF – OWL Lite S: ALC including transitivity of roles H: b t df H sub property, rdfs:subPropertyOf bP t Of I: owl:inverseOf (inverse roles) F: Functional Roles 51 WS 08/09 Wissenstechnologie @
  • 52. OWL –DL Reasoning Application Areas Taxonomy classification: Computes an inferred class hierarchy from the asserted definitions Consistency checking: Detects classes that cannot have any instances Instance classification: Finds all classes that a given individual belongs to State of the Art State-of-the-Art are so called tableaux algorithms for reasoning Worst case time compelxity is exponential, for practical problems usually faster 52 WS 08/09 Wissenstechnologie @
  • 53. DL Resources OWL Reasoning Examples Description Logic p g The Description Logic Handbook: Theory, Implementation, and Applications. F. Baader et al., Cambridge University Press, 2003. ISBN 0521781760 Press 2003 53 WS 08/09 Wissenstechnologie @
  • 54. DL (OWL) Reasoner Racer (commercial): FaCT++: Pellet: htt // ll t ldl / 54 WS 08/09 Wissenstechnologie @
  • 55. A Short Protege Demo Do you know mad Cows? 55 WS 08/09 Wissenstechnologie @
  • 56. Ontology Types and Existing Ressources Upper Level Ontologies Aka Top-Level Ontology, Foundation Ontology M d l of common objects Model f bj t Common Sense Knowledge/ General models of the World Domain Ontologies Model for a specific domain (i.e. Genes, Biomedical Engineering etc.) Focused also on th application use case F d l the li ti 56 WS 08/09 Wissenstechnologie @
  • 57. Upper Level Ontologies Formal Upper Level Ontologies Suggested Upper Merged Ontology (SUMO) DOLCE (Open)Cyc Basic Formal Ontology (BFO) … Informal Upper Level Ontologies DublinCore WordNet 57 WS 08/09 Wissenstechnologie @
  • 58. SUMO Suggested Upper Merged Ontology (SUMO) 1600.p1 From IEEE Working Group 1600 p1 Largest free, formal ontology available, with 20,000 terms and 70,000 axioms when all domain ontologies are , g combined. ( Mapping to Word Net Demo 58 WS 08/09 Wissenstechnologie @
  • 59. WordNet http://wordnet princeton edu/ Lexical Ontology for (English) Language Classes: Nouns, Verbs, Adjective, Adverbs G Grouped i t S d into Synsets t Relations between Synsets: hypernym, hyponym, holonym, meronym, troponym… holonym meronym troponym 220,000 Words; 128,000 Synsets Limitations No pronouncation and irregulary verbs No domain specific vocabulary 59 WS 08/09 Wissenstechnologie @
  • 60. Cyc Largest project to capture human knowledge Formalized representation of a vast quantity of fundamental human knowledge g Started 1986, Cycorp spin off 1994 Properitery System using predicate logic and LISP similar syntax Structured in micro theories and assertions Open Source Version available as OpenCyc htt // 60 WS 08/09 Wissenstechnologie @
  • 61. Cyc r/whatdoescycknow What Cyc „knows …. knows“ 61 WS 08/09 Wissenstechnologie @
  • 62. Summary OWL Syntax adds means to express complex classes and logics over RFDS OWL-DL,OWL-Lite, OWL-Full , , Formal Logical Theories for Reasoning Description Logic for OWL Abox, Tbox Upper Ontologies vs. Domain Ontologies SUMO, WordNet, OpenCyc Linking Open Data 62 WS 08/09 Wissenstechnologie @
  • 63. Points you should take away from this lecture • What OWL adds to RDFS? • Types of OWL and Reasoning capabilities? • Use existing Ontologies/Upper Level Ontologies • What is Linking Open Data? Next Week: • Ontology Modelling Rules of Thumb for modeling ontologies • Ontology Alignment & Matching • Semantic Web Frameworks: Jena/Sesame with Examples 63 WS 08/09 Wissenstechnologie @
  • 64. That‘s it for today… Thanks for your attention Questions/comments? i @ 64 WS 08/09 Wissenstechnologie @
  • 65. License This work is licensed under the Creative Commons Attribution 2.0 Austria License. To view a copy of this license, visit http://creativecommons org/licenses/by/2 0/at/ Contributors: Mathias Lux Peter Scheir Klaus Tochtermann Michael Granitzer 65 WS 08/09 Wissenstechnologie @