lecture 1: introduction

steelsquareInternet and Web Development

Oct 20, 2013 (4 years and 24 days ago)

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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


simply 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)

l
inked 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)

l
inked 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

l
inked data





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future web …


intelligent

representation

and processing of
data

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