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Primer Taller en Grid Computing Universidad del Valle, Cali, Colombia January 2007

Semantic Grid. Ontologies and the Semantic Web. www.ontogrid.eu. Oscar Corcho University of Manchester. Primer Taller en Grid Computing Universidad del Valle, Cali, Colombia January 2007. Outline. What is the Semantic Web The Syntactic and the Semantic Web Ontologies

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Primer Taller en Grid Computing Universidad del Valle, Cali, Colombia January 2007

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  1. Semantic Grid.Ontologies and the Semantic Web www.ontogrid.eu Oscar Corcho University of Manchester Primer Taller en Grid ComputingUniversidad del Valle, Cali, Colombia January 2007

  2. Outline • What is the Semantic Web • The Syntactic and the Semantic Web • Ontologies • Semantic Web Technologies • RDF, RDF Schema and OWL • Semantic Web Services Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  3. What is the Semantic Web • An extension of the current Web… • … where information and services are given well-defined and explicitly represented meaning, … • … so that it can be shared and used by humans and machines, ... • ... better enabling them to work in cooperation • How? • Promoting information exchange by tagging web content with machine processable descriptions of its meaning. • And technologies and infrastructure to do this Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  4. The Semantic Web Vision The Semantic Web The Syntactic Web • The Web was made possible through established standards • TCP/IP for transporting bits down a wire • HTTP & HTML for transporting and rendering hyperlinked text • Applications able to exploit this common infrastructure • Result is the WWW as we know it • Generations • 1st generation web mostly handwritten HTML pages • 2nd generation (current) web often machine generated/active • Both intended for direct human processing/interaction • In the next generation web, resources should be more accessible to automated processes • To be achieved via semantic markup • Metadata annotations that describe content/function Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  5. A place where computers do the presentation (easy) and people do the linking and interpreting (hard). Why not get computers to do more of the hard work? Where we are Today: the Syntactic Web Resource href href href Resource Resource Resource Resource href href href Resource href href href href Resource Resource Resource href href Resource Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  6. Hard Work using the Syntactic Web… Find images of Oscar Corcho …Malcolm Atkinson … David Fergusson … Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  7. What’s the Problem? • Typical web page markup consists of: • Rendering information (e.g., font size and colour) • Hyper-links to related content • Semantic content is accessible to humans but not (easily) to computers… Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  8. Information we can see… Primer Taller en Grid Computing Cali (Colombia) 15-18 Enero 2006 Organisers/sponsors/... ? UniValle, HP Curriculum Structured in four days Sessions each day Agenda for each day Session title Session speaker Session description Session slides and additional material … Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  9. Information a machine can see… WWW2002 The eleventh international world wide webcon Sheraton waikiki hotel Honolulu, hawaii, USA 7-11 may 2002 1 location 5 days learn interact Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire Register now On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed Tim berners-lee Tim is the well known inventor of the Web,… Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  10. Solution: XML markup with “meaningful” tags? <name>WWW2002 The eleventh international world wide webcon</name> <date>7-11 may 2002</date> <location>Sheraton waikiki hotel Honolulu, hawaii, USA</location> <introduction>Register now On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed</introduction> <speaker>Tim berners-lee <bio>Tim is the well known inventor of the Web,</bio> </speaker> <speaker>Tim berners-lee <bio>Tim is the well known inventor of the Web,</bio> </speaker> <registration>Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire<registration> Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  11. But What About…? <conf>WWW2002 The eleventh international world wide webcon</conf> <date>7-11 may 2002</date> <place>Sheraton waikiki hotel Honolulu, hawaii, USA</place> <introduction>Register now On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed</introduction> <speaker>Tim berners-lee <bio>Tim is the well known inventor of the Web,</bio> </speaker> <speaker>Tim berners-lee <bio>Tim is the well known inventor of the Web,</bio> </speaker> <registration>Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire<registration> Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  12. Still the Machine only sees… <>WWW2002 The eleventh international world wide webcon<> <>7-11 may 2002</> <>Sheraton waikiki hotel Honolulu, hawaii, USA<> <>Register now On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event … Speakers confirmed</> <>Tim berners-lee <>Tim is the well known inventor of the Web,</> </> <>Tim berners-lee <>Tim is the well known inventor of the Web,</> </> <>Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire<> Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  13. Outline • What is the Semantic Web • The Syntactic and the Semantic Web • Ontologies • Semantic Web Technologies • RDF, RDF Schema and OWL • Semantic Web Services Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  14. Need to Add “Semantics” • External agreement on meaning of annotations • E.g., Dublin Core for annotation of library/bibliographic information • Agree on the meaning of a set of annotation tags • Problems with this approach • Inflexible • Limited number of things can be expressed • Use Ontologies to specify meaning of annotations • Ontologies provide a vocabulary of terms • New terms can be formed by combining existing ones • “Conceptual Lego” • Meaning (semantics) of such terms is formally specified • Can also specify relationships between terms in multiple ontologies Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  15. Ontology in Computer Science • An ontology is an engineering artifact: • It is constituted by a specific vocabulary used to describe a certain reality, plus • a set of explicit assumptions regarding the intended meaning of the vocabulary. • Almost always including concepts and their classification • Almost always including properties between concepts • Similar to an object oriented model • Thus, an ontology describes a formal specification of a certain domain: • Shared understanding of a domain of interest • Formal and machine manipulable model of a domain of interest Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  16. Definitions of Ontologies (I) 1. “An ontology defines the basic terms and relations comprising the vocabulary of a topic area, as well as the rules for combining terms and relations to define extensions to the vocabulary” Neches R, Fikes RE, Finin T, Gruber TR, Senator T, Swartout WR (1991) Enabling technology for knowledge sharing. AI Magazine 12(3):36–56 2. “An ontology is an explicit specification of a conceptualization” Gruber TR (1993a) A translation approach to portable ontology specification. Knowledge Acquisition 5(2):199–220 Studer R, Benjamins VR, Fensel D (1998) Knowledge Engineering: Principles and Methods. IEEE Transactions on Data and Knowledge Engineering 25(1-2):161–197 3. “An ontology is a formal, explicit specification of a shared conceptualization” Guarino N, Giaretta P (1995) Ontologies and Knowledge Bases: Towards a Terminological Clarification. In: Mars N (ed) Towards Very Large Knowledge Bases: Knowledge Building and Knowledge Sharing (KBKS’95). University of Twente, Enschede, The Netherlands. IOS Press, Amsterdam, The Netherlands, pp 25–32 4. “A logical theory which gives on explicit, partial account of a conceptualization” Guarino N (1998) Formal Ontology in Information Systems. In: Guarino N (ed) 1st International Conference on Formal Ontology in Information Systems (FOIS’98). Trento, Italy. IOS Press, Amsterdam, pp 3–15 5. “A set of logical axioms designed to account for the intended meaning of a vocabulary”

  17. Outline • What is the Semantic Web • The Syntactic and the Semantic Web • Ontologies • Semantic Web Technologies • RDF, RDF Schema and OWL • Semantic Web Services Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  18. Ontology Languages OWL Inference RDFS Integration Integration RDF Annotation XML • Work on Semantic Web has concentrated on the definition of a collection or “stack” of languages. • Used to support the representation and use of metadata • Basic machinery that we can use to represent the extra semantic information needed for the Semantic Web RDF(S) Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  19. RDF • RDF stands for Resource Description Framework • It is a W3C Recommendation • http://www.w3.org/RDF • RDF is a graphical formalism ( + XML syntax + semantics) • for representing metadata • for describing the semantics of information in a machine- accessible way • Provides a simple data model based on triples. Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  20. The RDF Data Model • Statements are <subject, predicate, object> triples: • <Oscar,presents,SemanticGridSession> • Can be represented as a graph: • Statements describe properties of resources • A resource is any object that can be pointed to by a URI • The generic set of all names/addresses that are short strings that refer to resources • a document, a picture, a paragraph on the Web, http://www.cs.man.ac.uk/~ocorcho/index.html, a book in the library, a real person, isbn://0141184280 • Do not mistake them for Grid resources, though they could be the same, as we will see later in this talk!! • Properties themselves are also resources (URIs) presents Oscar SemanticGridSession Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  21. Linking Statements • The subject of one statement can be the object of another • Such collections of statements form a directed, labeled graph • The object of a triple can also be a “literal” (a string) “Oscar Corcho” hasName presents Oscar SemanticGridSession preparedBy hasHomePage preparedBy http://www.gs.unina.it/session-32.htm Pinar Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  22. RDF Syntax • RDF has an XML syntax that has a specific meaning: • Every Description element describes a resource • Every attribute or nested element inside a Description is a property of that Resource • We can refer to resources by URIs <rdf:Description rdf:about="some.uri/person/ocorcho"> <o:presentsrdf:resource="some.uri/session/SemanticGridSession"/> <o:hasName rdf:datatype="&xsd;string">Oscar Corcho</o:hasName> </rdf:Description> <rdf:Description rdf:about="some.uri/session/SemanticGridSession"> <o:hasHomePage>http://www.gs.unina.it/session-32.htm </o:hasHomePage> <o:preparedBy rdf:resource=“some.uri/person/ocorcho"> <o:preparedBy rdf:resource=“some.uri/person/pinar_alper"> </rdf:Description> Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  23. What does RDF give us? OWL Inference RDFS Integration Integration RDF Annotation XML • Single (simple) data model. • Syntactic consistency between names (URIs). • A mechanism for annotating data and resources. • Low level integration of data. RDF(S) Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  24. What doesn’t RDF give us? • RDF does not give any special meaning to vocabulary • Such as subClassOf or type (supporting OO-style modelling) • So, what’s the difference between this graph... • ... and this one? “Oscar Corcho” hasName presents Oscar SemanticGridSession preparedBy “Oscar Corcho” isAlsoKnownAs talksIn Oscar SemanticGridSession presentedBy Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  25. RDFS: RDF Schema • RDF Schema is another W3C Recommendation • http://www.w3.org/TR/rdf-schema/ • It extends RDF with a schema vocabulary that allows you to define basic vocabulary terms and the relations between those terms • Class, type, subClassOf, • Property, subPropertyOf, range, domain • it gives “extra meaning” to particular RDF predicates and resources • this “extra meaning”, or semantics, specifies how a term should be interpreted • The combination of RDF and RDF Schema is normally known as RDF(S) Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  26. RDFS simple example xsd:date eventDate Event subClassOf subClassOf subClassOf Personal_Event Local_Event Regional_Event involves Person subClassOf subClassOf Professor Researcher <?xml version="1.0" encoding="UTF-8"?> <rdf:RDF xml:base="http://www.ontogrid.net/StickyNote#" xmlns="http://www.ontogrid.net/StickyNote#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"> <rdfs:Class rdf:ID="Event"> <rdfs:subClassOf rdf:resource="http://www.w3.org/2002/07/owl#Thing"/> </rdfs:Class> <rdfs:Class rdf:ID="Local_Event"> <rdfs:subClassOf rdf:resource="#Event"/> </rdfs:Class> <rdfs:Class rdf:ID="Regional_Event"> <rdfs:subClassOf rdf:resource="#Event"/> </rdfs:Class> <rdfs:Class rdf:ID="Personal_Event"> <rdfs:subClassOf rdf:resource="#Event"/> </rdfs:Class> <rdfs:Class rdf:ID="Person"> <rdfs:subClassOf rdf:resource="http://www.w3.org/2002/07/owl#Thing"/> </rdfs:Class> <rdfs:Class rdf:ID="Professor"> <rdfs:subClassOf rdf:resource="#Person"/> </rdfs:Class> <rdfs:Class rdf:ID="Researcher"> <rdfs:subClassOf rdf:resource="#Person"/> </rdfs:Class> <rdf:Property rdf:ID="involves"> <rdfs:domain rdf:resource="#Personal_Event"/> <rdfs:range rdf:resource="#Person"/> </rdf:Property> <rdf:Property rdf:ID="eventDate"> <rdfs:domain rdf:resource="#Event"/> <rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#date"/> </rdf:Property> </rdf:RDF> Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  27. RDF(S) Inference rdfs:Class rdf:type Person rdf:type rdfs:subClassOf rdf:type Academic rdfs:subClassOf rdf:subClassOf Lecturer Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  28. RDF(S) Inference rdfs:Class rdf:type Academic rdf:type rdfs:subClassOf Lecturer rdf:type rdf:type Oscar Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  29. What does RDFS give us? • Ability to use simple schema/vocabularies to describe our resources • Consistent vocabulary use and sharing • Simple inference • Query mechanisms: SPARQL, SeRQL, RDQL, … • SELECT N FROM {N} rdf:type {sti:Event} USING NAMESPACE sti=<http://www.ontogrid.net/StickyNote#> • Examples • CS AktiveSpace • Lightweight schema to integrate data from University sites • myGrid • Service descriptions for e-Science Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  30. What doesn’t RDFS give us? • RDFS is too weak to describe resources in sufficient detail • No localised range and domain constraints • Can’t say that the range of hasEducationalMaterial is Slides when applied to TheoreticalSession and Code when applied to HandsonSession • TheoreticalSession hasEducationalMaterial Slides • HandsonSession hasEducationalMaterial Code • No existence/cardinality constraints • Can’t say: • Sessionsmust have some EducationalMaterial • Sessionshave at least one Presenter • No transitive, inverse or symmetrical properties • Can’t say that presents is the inverse property of isPresentedBy Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  31. The OWL Family Tree DAML RDF/RDF(S) DAML-ONT Joint EU/US Committee DAML+OIL OWL Frames OIL W3C OntoKnowledge+Others Description Logics Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  32. OWL • W3C Recommendation (February 2004) • A family of Languages • OWL Full • OWL DL • OWL Lite • Formal semantics • Description Logics (DL/Lite) • Relationship with RDF Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  33. OWL Basics (on top of RDF and RDFS) • Set of constructors for concept expressions • Booleans: and/or/not • A Session is a TheoreticalSession or a HandsonSession • Slides are not the same as Code • Quantification: some/all • Sessionsmust have some EducationalMaterial • Sessions can only have Presenters that have developed Grid applications or Grid middleware • Axioms for expressing constraints • Necessary and Sufficient conditions on classes • A Session that hasEducationalMaterialCode is a HandsonSession. • Disjointness • TheoreticalSessions are disjoint with HandsonSessions • Property characteristics: transitivity, inverse Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  34. OWL Ontology Example. BioPAX ontology • http://www.biopax.org/release/biopax-level2.owl Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  35. Reasoning Tasks • OWL DL based on a well understoodDescription Logic (SHOIN(Dn)) • Formal properties well understood (complexity, decidability) • Known reasoning algorithms • Implemented systems (highly optimised) • Because of this, we can reason about OWL ontologies • Subsumption reasoning • Allows us to infer when one class is a subclass of another • Can then build concept hierarchies representing the taxonomy. • This is classification of classes. • Satisfiability reasoning • Tells us when a concept is unsatisfiable • i.e. when it is impossible to have instances of the class. • Allows us to check whether our model is consistent. • Instance Retrieval/Instantiation • What are the instances of a particular class C? • What are the classes that x is an instance of? Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  36. Reasoning Tasks. Classification Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  37. What does OWL give us? • Ability to use complex schema/vocabularies to describe our resources. • Consistent vocabulary use and sharing. • Robust data integration techniques • Complex inference and several reasoning functions • Query mechanisms: OWL QL Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  38. Outline • What is the Semantic Web • The Syntactic and the Semantic Web • Ontologies • Semantic Web Technologies • RDF, RDF Schema and OWL • Semantic Web Services Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  39. The Semantic Web and the Semantic Web Services Semantic Web Services Web Services UDDI, WSDL, SOAP URI, HTML, HTTP WWW Semantic Web RDF, RDFS, OWL Web Services that describe their properties and capabilities using the vocabulary of an ontology, and they are expressed in some semantic markup language Dynamic Static Semantic richness Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  40. Discovery Automated Discovery services or workflows Knowledge assisted brokering & match making Guided instantiation and substitution Composition Automated Composition Self organising SOA Guided workflow assembly Composition (workflow) verification and validation Semantic Web Services Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  41. http://www.swsi.org/ OWL-S WSMO • OWL-WS WSDL-S Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  42. Semantic Web Services Instance of Instance of Ontologies Process <owl:Class rdf:ID="CompositeProcess"> <rdfs:subClassOf rdf:resource="#Process"/> <owl:disjointWith rdf:resource="#AtomicProcess"/> <owl:disjointWith rdf:resource="#SimpleProcess"/> ... Subclass of Subclass of Subclass of Composite Process Simple Process Atomic Process OWL-S instances <process:CompositeProcess rdf:ID=“buyMovieTicket”> <process:composedOf> <process:Sequence> <process:components rdf:parseType="Collection"> <process:AtomicProcess rdf:resource=“#findCinema" /> <process:AtomicProcess rdf:resource="#checkTimeTable" /> <process:AtomicProcess rdf:resource="#selectSeat” /> <process:AtomicProcess red:resource=“#buyTicket” /> ... Knowledge level Oscar Corcho. Primer taller de Grid Computing. Cali, Colombia, January 2007

  43. Semantic Grid.Ontologies and the Semantic Web www.ontogrid.eu Oscar Corcho University of Manchester Primer Taller en Grid ComputingUniversidad del Valle, Cali, Colombia January 2007

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