Semantic Web

woodruffpassionateInternet και Εφαρμογές Web

21 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

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1

Semantic Web


The Semantic Web provides a common framework
that allows data to be shared and reused across
application, enterprise, and community boundaries. It
is a collaborative effort led by W3C with participation
from a large number of researchers and industrial
partners. It is based on the Resource Description
Framework (RDF),
which integrates a variety of
applications using XML for syntax and URIs for
naming.



http://www.w3.org/2001/sw/

(Semantic Web homepage, 2004)

(unchanged, April 23, 2006, December 3, 2007 pink text no longer there…)


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Semantic Web


The Semantic Web is the representation of
data on the World Wide Web. It is a
collaborative effort led by W3C with
participation from a large number of
researchers and industrial partners… based
on RDF…integrates…applications using XML
…for naming.

http://www.w3.org/2001/sw/

(Semantic Web homepage, 2003)


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Semantic Web


The
Semantic Web

is the abstract
representation of
data

on the World Wide
Web, based on the RDF standards and other
standards
to be defined
. It is
being developed

by the W3C, in collaboration with a large
number of researchers and industrial
partners.

http://www.w3.org/2001/sw/

(Semantic Web homepage, 2002)


4

Another definition for the Semantic Web


An extension of the current web in
which information is given well
-
defined
meaning, better enabling computers
and people to work in cooperation.


….
Berners
-
Lee, T., Hendler, J., Lassil, O. (2001)
The Semantic Web. Scientific American.





Agents perform tasks (you read!)

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The Semantic Web


Berners Lee, T. (1999).
Weaving the
Web
.


A dream “where machines become
capable of analyzing all the data on the
Web


the content, links, and transactions
between people and computers….”a
‘Semantic Web’…would make this
possible.”



Dan Connolly (1998)



“Relieve him from the ‘bane of my [his]
existence’”..performing mundane tasks that
he knows a computer can perform for him

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A
VISION….


VISION


Shared vision


Inspired by a host of creative thinkers


Vannevar Bush’s MEMEX (1945)


Alan Turing
-

Turing Machine


Project Xanadu (
http://xanadu.com/
)


Mission statement: DEEP INTERCONNECTION,
INTERCOMPARISON AND RE
-
USE

7

Berners
-
Lee
(http://www.w3.org/2000/Talks/1206
-
xml2k
-
tbl/slide10
-
0.html)



8

Questions…


Why would we want a Semantic
Web?


Issues…


Old wine in a new bottle?





Do we have elements of the semantic web in
place yet? (table for later)

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What could the Semantic Web
do?


SOLVE PROBLEMS


Arrange a vacation


Schedule an doctors appointment


HELP with environmental monitoring


Link GIS and field data to give a reading


Pine trees with brown leaves in spring, by the
waste plant.


Other ideas?


10

Current limitations


Vast majority of web content is not
semantically encoded


Humans easily read and interact with web
content retrieved via web browsers


Percentage of web resources linking to
ontological knowledge structures and
metadata…insufficient to support
widespread agent navigation



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Current limitations


Knowledge about the Semantic Web is
limited


Much time spent on vision and model


Semantic Web technologies and
languages being developed,
inconsistent


Buy
-
in?

12

What needs to be done (organizing
information context)


Meaning needs to be expressed!


Semantics need to be established


Metadata schemas (vocabularies) and ontologies


INCREASED ONTOLOGICAL COMMITMENTS


TRUSTED METADATA


Agreements need to be reached on
languages to support


Logic to support inferencing among semantics,
conduct tasks

(work in progress, W3C, tools, etc.)


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Semantic Web Languages


A Semantic Web language must describe
meaning in a machine
-
readable way


Specify vocabulary through an ontology or a
schema


OWL


The standard ontology language permits the encoding of
data and rules for reasoning about the data.
Think
simple: “if then



Formally define the vocabulary in a way that it will
work in automated reasoning


The vocabulary must be extensible (evolving tool)

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Ontologies


Taxonomies + set of inference rules


(a car is a type of vehicle)


+ Axioms for more complex definitions
(
constraints on the possible interpretations for the
defined terms
)


A car is a type of vehicle that is used for transportation


A car is not a truck, bus, bicycle, or scooter, which are
vehicles that are also used for transportation


Automobile is super
-
ordinate concept for car


Toyota, Honda, and Ford are car brands


Specific models, such as a Honda Civic
DX
is a sub
-
ordinate
concept

15

Semantic Web Languages/Technologies,
need to supported


Resource Description Framework (RDF)
[foundational language]


Simple HTML Ontology Extension (SHOE)
[used as a testbed over the past 5 years,
U.Maryland]


DAML+OIL


Ontology Inference Layer (OIL)


Defense Advanced Research Projects Agency’s
Agent Markup Language (DAML) [under
development, combines best features of the
others]


OWL (
Ontology Working Group Language
)

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Semantic Web Services


Services that buy into the Semantic
Web


Support Semantic Web infrastructure


Support tasks such as:


Automatic
Discovery


Automatic
Execution


Automatic
Interoperation


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Semantic Web Services

Service Discovery example:

“Find service that sells airline tickets from
Raleigh to Honolulu and that will
accepts payment by my American
Express credit card”

Based on: Semantic Web Services / S.A. McIlraith et al., 2001

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Semantic Web Services

Service Execution example:

“Buy me a ticket from
www.expedia.com

on United flight 1234 from Raleigh to
Honolulu for December 25, 2006”

19

Service Interoperation example
(able to
connect the dots… b/c of
interoperability)

“Made the travel arrangements for my
Honolulu trip for this coming December

Semantic Web Services

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Semantic Web Applications


ORACLE:
http://www.oracle.com/technology/tech/semantic_
technologies/index.html


MusicBrainz:
http://musicbrainz.org/
; A Semantic
Web Service
http://logicerror.com/musicbrainzArticle


Semantic Web environmental directory:
http://www.swed.org.uk/swed/index.html

(search
“biodiversity)


NCI Thesaurus:
http://www.mindswap.org/2003/CancerOntology/


Physnet:
http://www.physnet.de/PhysNet/

(Topics, 30, view rdf)

21

Berners Lee, et al.


To date, the World Wide Web has
developed most rapidly as a medium of
documents for people rather than of
information that can be manipulated
automatically. By augmenting Web
pages with data targeted at computers
and by adding documents solely for
computers, we will transform the Web
into the Semantic Web.

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Questions…


Do we have elements of the
semantic web in place yet?