semantic web - an introduction by daniel wu (danielwujr)
TRANSCRIPT
Semantic Web - an introduction
By Daniel Wu (danielwujr)
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
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
Semantic?
• Assalamu alaikum
• Let’s give it semantic…– Assalamu alaikum is Arabian– Assalamu alaikum means “Hello”
• sēmantikós (Greek) = having meaning
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.)
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
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
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.
• Source: W3C Semantic Web FAQ
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;
SW Features & Services (cont.)
• However…– You probably won’t “see” SW– And this is Weak AI
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
SW Knowledge Representation & Layers
Semantic Web Layer Cake
• 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
• EXtensible Markup Language (XML)
– XML provides a surface syntax for structured documents
– XML imposes no semantic constraints on the meaning of documents
• 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
• 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
• 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.
Ontology
• Definition
• Example
• Ontology & Knowledge presentation
• Ontology & Building ontology
• Ontology & Folksonomy
• Ontology & Interoperability
Ontology - Definition
• (short version)– Ontologies are systems of formally defined related co
ncepts.
• (long version)– Ontologies define the concepts and relationships use
d 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.
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 perso
n 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.
Ontology & Knowledge presentation
– Back to “Assalamu alaikum”– We need previous knowledge to fully unders
tand the concept of “Assalamu alaikum”– previous knowledge
= world view
= ontology
– Oh! “Assalamu alaikum” means “Hello”
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!
Ontology & Folksonomy
• Can ontology not be hierarchical?
• Can ontology be built from folksonomy?
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.
Interoperability between different ontologies
Interoperability between different ontologies
• 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
• 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.
• Logic and Proof
– Tools to query language for semantic web data sources
– DL (Description Logic), not FOL
• Trust and Digital signature
– Documents be parsed not just into trees of assertions, but into trees of assertions about who has signed what assertions.
SW Layers - Review
Semantic Web Layer Cake
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
SW Current Status
• Bump!– Tools problem– Ontology problem– Poor rule engine
performance
SW Current Status
• Important players - Google– Not taking actions– Ask question!
• Incompetence• Competition• Deception
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
Q & A
• Welcome!