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lecture 1: introduction

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the semantic web vision today�s web (1)

web content – for human consumption (no structural information)

people search for information, keep in touch with other people, make purchases, look for entertainment … minimal support by software tools

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the semantic web vision today�s web (2)

keyword-based search engines … with some problems:

!  high recall & low precision – too many documents retrieved !  low/no recall – no relevant documents found !  results sensitive to vocabulary – similar words not considered !  results are single web pages – �distributed� information not

retrieved !  human needed for interpretation, no other software tools use the

result

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the semantic web vision today�s web (3)

a problem with semantics … so … a need for different representation of information, and intelligence that takes advantage of that

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the semantic web vision … the future (1)

knowledge management !  key activity of large businesses (knowledge seen

as intellectual asset) !  information is in a weakly structured form !  problems with: sharing, extracting, marinating,

viewing

Semantic Web -> knowledge organized, tools for knowledge maintenance, query answering tools

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the semantic web vision … the future (2)

business-to-customer electronic commerce !  browsing on-line shops, selecting the best

alternative/offer -> time and effort consuming activity

!  decisions making based on limited/partial information

Semantic Web -> software �shopping� agents able to interpret the product information and the terms of service, and conduct negotiations

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the semantic web vision … the future (3)

business-to-business electronic commerce !  data exchange using the Electronic Data Interchange

(EDI) approach (complex, isolated) !  lack of standards

Semantic Web -> differences in terminology resolved (abstract domain models), automatic translation of services, auctioning, negotiations, and drafting of contracts

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the semantic web vision … the future (4)

wikis !  collections of pages that allow users to add content

(collaborative knowledge creation)

Semantic Web -> usage of semantic technologies (enriching structured text and untyped hyperlinks with semantic annotation referring to an underlying model of the captured knowledge)

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the semantic web vision … the future (5)

personal agents: a future scenario

Michael has some neck pain, he asked his Semantic Web agent to arrange for him physical therapy sessions which were suggested by Michael�s physician …

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semantic web technologies metadata (1) HTML is the predominant language used for writing web pages

humans have no problem reading it machines are not able to distinguish different people, things, follow links to find out more about topics – simple they have no clue what a given text is about

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semantic web technologies metadata (2)

<company> <companyName>… </companyName> <staff> <director> … </director> <viceDirector> … </viceDirector> </staff> </company>

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semantic web technologies metadata (3) HTML is replaced by a language that carries information about a content

metadata – data about data, capture part of the meaning of data (tags that are �defined� in a systematic way)

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semantic web technologies ontology (1) study of nature of existence, how to describe things that actually exist

world is made up of specific objects that can be grouped into abstract classes based on shared properties

it describes a domain of interest

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semantic web technologies ontology (2) consists of a finite list of terms and the relationships between them

terms denote concepts (classes of objects) of the domain

relationships include hierarchies of classes + properties of objects, value restrictions, logical relationships between objects

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semantic web technologies ontology (3) provide �a shared understanding of a domain� overcome differences in terminology

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semantic web technologies ontology languages RDF – is a data model for objects and relations between them

RDF Schema – a description language for describing properties and classes of RDF resources, provides a semantics for generalization hierarchies

OWL – a rich language for describing properties and classes, and relations between them

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semantic web versus AI logic (1) provides principles of reasoning provides well-understood formal semantics �unlocks� automated reasoners leads to uncovering ontological knowledge given implicitly

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semantic web versus AI logic (2) used by intelligent agents for making decisions and selecting courses of action

provides explanations for conclusions

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semantic web versus AI logic (3) SWRL – semantic web rule language for constructing rules based on ontology classes and relationships

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semantic web versus AI agents (1) software agents work autonomously and proactively

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semantic web versus AI agents (2) tasks of personal software agent in SW: !  receive tasks and preferences from users !  seek information on the web, communicate with other

agents !  compare information from different sources, make choices !  give answer to users

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semantic web versus AI agents (3) metadata !  identify and extract information

ontology !  web search, information interpretation !  communication with other agents

logic !  information retrieval, conclusion derivation

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a layered approach development of SW in steps

each step building a layer on the top of another

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a layered approach

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a layered approach

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alternative stack

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a layered approach XML layer !  syntactic basis

RDF layer !  basic data model for facts !  RDF Schema simple ontology language

ontology layer !  more expressive languages - OWL

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a layered approach logic layer !  enhance ontology, application specific knowledge

proof layer !  proof generation, validation

trust layer !  digital signature, rating agents …

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the semantic web vision … the present (1)

linked data

a new paradigm built on one of the layers of SW – RDF core

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the semantic web vision … the present (2)

linked data

each piece of information is linked to other pieces different types of links different sources of data

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the semantic web vision … the present (3)

linked data

every piece of information presented as a triple: subject-property-object

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the semantic web vision … the present (4)

linked data

a vast, interconnected web of triples (pieces of information)

easy to query with SPARQL – a special query language for RDF

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the semantic web vision … linked data

linked data

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future web …

intelligent representation and processing of data

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