1. Semantic Web - an introduction By Daniel Wu (danielwujr)

2. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

3. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

4. Semantic? Assalamu alaikum Let’s give it semantic… –Assalamu alaikum is Arabian –Assalamu alaikum means “Hello” sēmantikós (Greek) = having meaning

5. Problem Definition Computer have no reliable way to process semantics on Web content. (Most of the Web’s content today is designed for humans to read.)

6. Semantic Web (SW) Proposal Tim Berners-Lee –inventor of the WWW 1998 Solution 1.Achieving a set of connected applications for data on the Web in such a way as to form a consistent logical web of data. 2.Develops languages for expressing information in a machine- processable form. - Semantic Web Road map, Tim Berners-Lee

7. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

8. SW Features & Services Semantic Web The semantic web is an evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily.World Wide Webweb contentnatural language software agentsintegrate Source: W3C Semantic Web FAQ

9. SW Features & Services (cont.) Benefits –data integration, whereby data in various locations and various formats can be integrated in one, seamless application; –resource discovery and classification (vertical search) provide better, domain specific search engine capabilities; –cataloging describing the content and content relationships available at a particular Web site, page, or digital library; –intelligent software agents facilitate knowledge sharing and exchange;

10. SW Features & Services (cont.) However… –You probably won’t “see” SW –And this is Weak AI

11. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

12. SW Knowledge Representation & Layers Semantic Web Layer Cake

13. Uniform Resource Identifiers (URI) –URI is a name. (a pointer) –Uniform Resource Locator (URL) is one form of URI –URI does not need to be accessible over the Internet

14. EXtensible Markup Language (XML) –XML provides a surface syntax for structured documents –XML imposes no semantic constraints on the meaning of documents

15. Resource Description Framework (RDF) –RDF is a simple data model for referring to objects ("resources") and how they are related. –RDF enable anyone to say anything about anything –Triples: subject, predicate, object –RDF is composed of URIs –Ex. Daniel study CS

16. RDF schema –RDF Schema is a vocabulary for describing properties and classes of RDF resources, with a semantics for generalization-hierarchies of such properties and classes. –Ex. Dog SubClassOf Animal

17. Web Ontology Language (OWL) –OWL adds more vocabulary for describing properties and classes: among others, relations between classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.

18. Ontology Definition Example Ontology & Knowledge presentation Ontology & Building ontology Ontology & Folksonomy Ontology & Interoperability

19. Ontology - Definition (short version) –Ontologies are systems of formally defined related concepts. (long version) –Ontologies define the concepts and relationships used to describe and represent an area of knowledge. Ontologies are used to classify the terms used in a particular application, characterize possible relationships, and define possible constraints on using those relationships.

20. Ontology - Example A company is a type organization. An organization may have a product or a service. An organization is a group of people. An employer may be a person or an organization. A person may be employed by an employer. A person may be in a marriage with only one other person at a time. A marriage is a kind of romantic relationship. A friendship is a kind of social relationship. A romantic relationship is a kind of friendship. A person may be socially related to another person. A person must have a gender.

21. Ontology & Knowledge presentation –Back to “Assalamu alaikum” –We need previous knowledge to fully understand the concept of “Assalamu alaikum” –previous knowledge = world view = ontology –Oh! “Assalamu alaikum” means “Hello”

22. Ontology & Building ontology Cyc –Top down approach –Defines ontology on its own –Centralized Semantic Web –Bottom up approach –Defines language to define ontology –Destributed Everyone defines his/her own ontologies!

23. Ontology & Folksonomy Can ontology not be hierarchical? Can ontology be built from folksonomy?

24. Interoperability between different ontologies The OWL language can express mappings between concepts in different ontologies. But if there are many ontologies, and many of them partially overlap, it is a non-trivial task to actually make the mappings between their concepts.

25. Interoperability between different ontologies

26. However… It’s hard. Having same name doesn’t guarantee having same meaning A bad example… – 嘟嚕嘟嚕嘟嚕嘟嚕達達達 Wrong conversion… Same name doesn’t guarantee same meaning

27. Web Ontology Language (OWL) –OWL adds more vocabulary for describing properties and classes: among others, relations between classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.

28. Logic and Proof –Tools to query language for semantic web data sources –DL (Description Logic), not FOL

29. Trust and Digital signature –Documents be parsed not just into trees of assertions, but into trees of assertions about who has signed what assertions.

30. SW Layers - Review Semantic Web Layer Cake

31. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

32. SW Current Status Bump! –Tools problem –Ontology problem –Poor rule engine performance

33. SW Current Status Important players - Google –Not taking actions –Ask question! Incompetence Competition Deception

34. Presentation Outline (Why)Problem Definition (Who and When)Semantic Web (SW) Proposal (What)SW Features & Services (How)SW KR* & Layers (Where)SW Current Status *knowledge representation

35. Q & A Welcome!