Chapter 5 semantic web
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This document discusses knowledge representation and description logic. It introduces description logic as a logic-based knowledge representation technique that uses concepts, roles, and individuals to describe domains. Description logics allow constructing complex concepts from basic concepts and roles. Common description logics include ALC, which can represent concepts using operators like union and intersection. Description logics also use taxonomy to represent class subsumption and inference systems to reason about knowledge.
![F-Logic
ABC[hasLegalName -> ‘ABC Travel Agency’,
hasOfficesIn ->> {Bangalore, Mumbai},
hasPhones ->> {00918023514537, 0091223885270},
hasEmployees ->> {Anita, Sunita, Punita}].
Anita[hasName -> ‘Miss Anita’,
hasAddress -> AddressAnita[hasStreet -> ‘Nariman Point’,
hasNumber -> 320,
hasCity -> Mumbai].
BookingABCAnita[bookedBy -> ABC,
bookedFor -> Anita,
issuedFor -> LH635].
Akerkar: Foundations of © Narosa Publishing House, 2009 14
Semantic Web.](https://image.slidesharecdn.com/chapter5semanticweb-110905083500-phpapp02/85/Chapter-5-semantic-web-14-320.jpg)
![Company :: LegalEntity.
Company[hasLegalName => STRING,
hasOfficesIn =>> City,
hasPhones =>> NUMBER,
hasEmployees =>> Person].
Person :: LegalEntity.
Person[hasName => STRING,
hasAddress => Addresss].
Employee :: Person.
Employee[isEmployedAt => Company].
Booking[bookedBy => LegalEntity,
bookedFor => Person,
issuedFor => Flight].
ABC : Company.
Anita : Person.
LH635 : Flight.
BookingABCAnita : Booking.
Akerkar: Foundations of © Narosa Publishing House, 2009 15
Semantic Web.](https://image.slidesharecdn.com/chapter5semanticweb-110905083500-phpapp02/85/Chapter-5-semantic-web-15-320.jpg)
Chapter 5 semantic web
- 1. Chapter 5Knowledge Representation & Description Logic
- 2. Introduction • Logic based Knowledge Representation formalisms – Descendants of semantic networks – KL-ONE – Domain description in the form of concepts (classes), roles (properties, relationships) and individuals. – A knowledge base (KB) is a pair K = < A> where T T, , is a TBox, and A is an Abox. Akerkar: Foundations of © Narosa Publishing House, 2009 2 Semantic Web.
- 3. Introduction • Description Logic: set of concept and role forming operators – ALC is a type of description logics. – Concepts constructed using u, t, :, 9 and 8 • S used for ALC with transitive roles (R+) Akerkar: Foundations of © Narosa Publishing House, 2009 3 Semantic Web.
- 4. DL Architecture Knowledge Base =============== Inference Interface Tbox (schema) System Abox (data) Akerkar: Foundations of © Narosa Publishing House, 2009 4 Semantic Web.
- 5. Syntax & Semantics ALC provides two special classes as shortcuts: Akerkar: Foundations of © Narosa Publishing House, 2009 5 Semantic Web.
- 6. Example 5.11 Akerkar: Foundations of © Narosa Publishing House, 2009 6 Semantic Web.
- 7. ALC Description Logic • Two kinds of concept descriptions – elementary descriptions and – complex descriptions • ALC concept formulas are built up from basic concept names and roles. • ALC statements relate named or anonymous concepts by means of one of the following: – Inclusion, – inverse inclusion, and – Equivalence. Akerkar: Foundations of © Narosa Publishing House, 2009 7 Semantic Web.
- 8. Reasoning About Knowledge • Description logics uses tableau algorithms – for deciding concept satisfiability with respect to a knowledge base. – A tableau algorithm for a DL language contains the following elements: • A completion graph, known as tableau, which represents a model of the DL language. • A set of tableau expansion rules to construct a complete and consistent completion graph. • A set of blocking rules to detect infinite cyclic models and ensure termination. • A set of clash conditions to detect logic contradictions. Akerkar: Foundations of © Narosa Publishing House, 2009 8 Semantic Web.
- 9. CLASSIC • Example 5.1: Express the sentences in the CLASSIC language. – The set of men with at most two daughters. AND(Man, AT-MOST(2, Daughter). – The set of men with at most two daughters who are all professors in physics or mathematics departments. AND(Man, AT-MOST(2, Daughter)), ALL(Daughter, AND(Professor, FILLS(Department, Physics, Mathematics))). Akerkar: Foundations of © Narosa Publishing House, 2009 9 Semantic Web.
- 10. CLASSIC & OWL • CAR = AND (FOURWHEELER, ALL (hasMaker, FACTORY)). <owl:Class rdf:ID="Car"> <rdfs:subClassOf rdf:resource="&vehicle;FourWheeler" /> ... <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource="#hasMaker" /> <owl:allValuesFrom rdf:resource="#Factory" /> </owl:Restriction> </rdfs:subClassOf> ... </owl:Class> Akerkar: Foundations of © Narosa Publishing House, 2009 10 Semantic Web.
- 11. • CAR = AND (FOURWHEELER, AT-LEAST (1 engine)) <owl:Class rdf:ID="Car"> <rdfs:subClassOf rdf:resource="&vehicle;FourWheeler"/> <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource="#hasEngine"/> <owl:minCardinality rdf:datatype="&xsd;nonNegativeInteger">1</owl:minCardinality> </owl:Restriction> </rdfs:subClassOf> ... </owl:Class> Akerkar: Foundations of © Narosa Publishing House, 2009 11 Semantic Web.
- 12. • SCOOTYPEPPLUS = AND (TWOWHEELER, FILLS (hasColour Pink)) <owl:Class rdf:ID="ScootyPepPlus"> <rdfs:subClassOf rdf:resource="#TwoWheeler"/> <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource="#hasColour" /> <owl:hasValue rdf:resource="#Pink" /> </owl:Restriction> </rdfs:subClassOf> </owl:Class> Akerkar: Foundations of © Narosa Publishing House, 2009 12 Semantic Web.
- 13. Rule Languages • RuleMarkup in XML • WSML Akerkar: Foundations of © Narosa Publishing House, 2009 13 Semantic Web.
- 14. F-Logic ABC[hasLegalName -> ‘ABC Travel Agency’, hasOfficesIn ->> {Bangalore, Mumbai}, hasPhones ->> {00918023514537, 0091223885270}, hasEmployees ->> {Anita, Sunita, Punita}]. Anita[hasName -> ‘Miss Anita’, hasAddress -> AddressAnita[hasStreet -> ‘Nariman Point’, hasNumber -> 320, hasCity -> Mumbai]. BookingABCAnita[bookedBy -> ABC, bookedFor -> Anita, issuedFor -> LH635]. Akerkar: Foundations of © Narosa Publishing House, 2009 14 Semantic Web.
- 15. Company :: LegalEntity. Company[hasLegalName => STRING, hasOfficesIn =>> City, hasPhones =>> NUMBER, hasEmployees =>> Person]. Person :: LegalEntity. Person[hasName => STRING, hasAddress => Addresss]. Employee :: Person. Employee[isEmployedAt => Company]. Booking[bookedBy => LegalEntity, bookedFor => Person, issuedFor => Flight]. ABC : Company. Anita : Person. LH635 : Flight. BookingABCAnita : Booking. Akerkar: Foundations of © Narosa Publishing House, 2009 15 Semantic Web.
- 16. Tools & Reasoners – Protégé: a free, open source ontology editor and a knowledge acquisition system. – OntoEdit – KAON2 – Pellet – FaCT+ – SESAME – OWL Validator Akerkar: Foundations of © Narosa Publishing House, 2009 16 Semantic Web.
- 17. Suggested Readings 1. F. Baader, D. Calvanese, D. McGuinness, D. Nardi, and P. Patel-Schneider, editors. The Description Logic Handbook: Theory, Implementation and Applications. Cambridge University Press, 2003. 2. R. J. Brachman and al. Living with classic: When and how to use a kl-one-like language. In John Sowa, editor, Principles of Semantic Networks: Exploration in the Representation of Knowledge, pages 401--456. Morgan Kaufmann, 1991. 3. I. Horrocks, U. Sattler, Ontology reasoning in the SHOQ(D) description logic, in: Proc. of the 17th Int. Joint Conf. on Artificial Intelligence (IJCAI 2001), pp. 199–204, 2001. 4. I. Horrocks, P. F. Patel-Schneider, S. Bechhofer, and D. Tsarkov. OWL Rules: A Proposal and Prototype Implementation. Journal of Web Semantics, 3,1, 2005. 5. B. Motik, U. Sattler, and R. Studer. Query Answering for OWL- DL with Rules. Journal of Web Semantics 3,1, 2005. http://www.Websemanticsjournal.org/ps/pub/2005-3. Akerkar: Foundations of © Narosa Publishing House, 2009 17 Semantic Web.