Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

-­‐  the  technology  behind  Web  3
...
ac
...

CO7216 Semantic Web

4  

External Resources
—  W3C website:

http://www
...
org/standards/semanticweb
—  Additional material on the Blackboard
—  Some books
—  Grigori Antoniou, Frank van Harmelen, A Semantic Web

Primer, MIT Press, USA, 2008
...

—  Semantic Web for the Working Ontologist, Dean
Allemang, Jim Hendler, Morgan Kaufmann, 2nd edition
...

—  More can be found at: http://www
...
org/wiki/SwBooks
CO7216 Semantic Web

5  

Prerequisites

—   Good  understanding  of  XML  and  XML  Schema    

CO7216 Semantic Web

6  

Introduction  to  
the  Semantic  Web    

7  

The “Current” Web
—  Tim Berners Lee (amongst others) invented the WWW
...

—  Essential: The idea of an open community
—  HTML is typically the language used to code information
...
html HTTP/1
...
somehost
...
html
—  Markup language which displays data in a form “humans” can
interpret it: HTML (often styled with CSS)
— 






This is my first homepage
...

—  A library of documents (web pages) connected by links
...
Graphics,
—  multimedia, text, links
...


—  Computers: Presentation-easy
...

—  Tools are available to
—  author web pages (HTML editors)
...

—  interpreting web pages (??????)
CO7216 Semantic Web

10  

Page  1  

The Linked “Syntactic” Web
•  The  hyperlinks  defines  a  relationship  
between  the  current  page  and  the  target  
•  link  text  describes  the  destination  content  
 
 
http://…/page1
...
html  
 
href  
href  
href  

http://…/page1
...
/homepage
...
html  
CO7216 Semantic Web

11  

Searching the Syntactic Web: Hard Work!
—  What you want may not be “exactly” what you get
...


mouse, cat

Paris Hilton
CO7216 Semantic Web

12  

Searching the Syntactic Web: Hard Work!
—  Success of the Web -> Search Engines, but …
...

—  Information overload: The complexity and volume of search results is

too large to be handled by humans
...
g
...
Too much is as bad as too little
...

—  Most searches target only single web pages
...

—  Extracting data from repositories:
—  Online shopping, job hunting etc
...
g
...

CO7216 Semantic Web14  

Problems with the “current” web
—  Web pages do not contain information about their content
...

—  The meaning or semantics of Web content can be

interpreted only by humans
Amazon as seen by computer:    
 

%£$^%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£
$^%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£$^
%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£$^%^$
£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£$^%^$£&$
%^$^&%&^&%&^%))(@*£&(&£(*&££@  
%£$^%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£
$^%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@%£$^
%^$£&$%^$^&%&^&%&^%))(@*£&(&£(*&££@  
 
CO7216 Semantic Web

16  

XML: A possible solution?
—  Developed within W3C
—  Allows for extensibility

Accompanied by much related work:
—  XML Schemas /cf DTDs
—  XML Namespaces
—  XLink and XPointer:Better hyperlinking
—  XSLT: Transform XML resources XPath: query XML
documents
—  Markup documents with “meaningful” tags !!!

CO7216 Semantic Web

17  

Problems with XML
John Smith’s homepage is http://www
...
le
...
uk/johnsmith
This information could be typically be represented in XML according to
different XML schemas:
 
1  

2  

3  

4  


http://www
...
le
...
uk/johnsmith
John Smith



John Smith

John Smith

To    a  person  reading    
these,  these  
representations  mean  
the  same  thing  


CO7216 Semantic Web

18  

Problems with XML
John Smith’s homepage is http://www
...
le
...
uk/johnsmith
This information could be typically be represented in XML according to
different XML schemas:
 

 

John Smith

The  above  XML  document    

as  seen  by  an  XML  parser  


 





text1




parser  

CO7216 Semantic Web

Human    can  read  and  
understand  the  meaning  
of  this  document  
because  the  element  
names  are  a  big  hint  for  
a  human  reader  
 
Even  if  computer  knows  
the  document  schema  (a  
big  if),  the  meaning  of  
the  document  is  still  not  
clear
...

—  Does not provide semantics (what does mean?)
—  XML is commonly depicted as “self-documenting” but this

depiction ignores critical ambiguities
...

—  The hierarchical model for representation is limited
...
g
...

Requirements: You want to rent a room in a house or flat in Leicester, close to
 
the university and you can afford up to £400 pm including all bills paid
...

Estate Agents Web site: Estate Agent uses the following to describe what is
available
...


 

Rent
Leicester
10 mins
400
Students
Yes


 
Difficult to answer the question using XQuery, although structured information
is provided
...

CO7216 Semantic Web

23  

What’s missing? Semantics!!

“  

The bane of my existence is doing things that I know the
computer could do for me
...

—  Tim Berners Lee - two part vision for the Web
—  to make the web more collaborative
...

—  Historically data was locked away behind proprietary

applications
...

—  Machine processable data has to be smart data
CO7216 Semantic Web

25  

What is Semantic Web

Semantic Web is a logical extension of the current web in
which information is given well-defined meaning, better
enabling computers and people to work in cooperation
...
It is a
collaborative effort led by W3C with participation from a
large number of researchers and industrial partners
...


• Semantic web
• Knowledge representation
• Machine readable and understandable
• Semantics (Ontology)
• RDF, OWL etc

The Semantic Web is an extension of the current Web and not its replacement
...

—  Solving the Application Integration problem
...

—  A connected web - a smarter web
...
w3
...


CO7216 Semantic Web

29  

http://www
...
org/RDF/FAQ  

Semantic Web Applications
—  Data integration; describing collections of pages that

represent a single logical “document”
—  Allows intelligent software agents to facilitate knowledge
sharing and exchange
—  Annotating content and describing content relationships
—  Resource discovery and classification
—  Semantic search engine

CO7216 Semantic Web

30  

http://www
...
org/RDF/FAQ  

Semantic Web Uptake
—  Semantic Web is NOT just for research community
...

Oracle Spatial and Graph RDF Semantic Graph
—  Microsoft Bing Satori knowledge base
—  Google Knowledge Graph
—  UK Government project to make available non-personal UK
government data as open data (Data
...
uk )
Many EU/UK organisations and research projects have already used
Semantic Web technologies
...

— 

CO7216 Semantic Web

31  

Summary
—  Semantic Web is not a replacement of the current Web, it

is an evolution of it
—  Semantic Web is about:
—  Annotation of data on the Web data linking on the Web
—  Data Integration over the Web
—  Semantic Web aims at automating tasks currently carried out by

humans

—  Semantic Web is becoming real (maybe not as we

originally envisioned it, but it is)

CO7216 Semantic Web

32  

Essential Reading
—  Chapter 1 of the recommended books (Lecture Notes,

page 5)
—  W3C Semantic Web Frequently Asked Questions:
http://www
...
org/RDF/FAQ
—  Scientific American article (Blackboard -> Web Links)

CO7216 Semantic Web

33  

Infrastructure  for    
the  Semantic  Web    

34  

http://www
...
org/2001/sw/  

Infrastructure for the Semantic Web  
Semantic Web Layer Cake  

CO7216 Semantic Web

35  

Semantic Web Technologies
—  Explicit Metadata (about “structuring” the data, It

describes characteristics about the resource in a
structured way)
—  Ontologies to standardise concepts and relations
between them
—  Logic and Inference: languages founded in various
flavours of logic
—  Software Agents: make use of all the above to help us
in our tasks

CO7216 Semantic Web

36  

Semantic Web Layer Cake  

CO7216 Semantic Web

37  

URL vs URI vs IRI
—  URL (Uniform Resource Locator)
—  A reference (an address) to a resource on the Internet
...

—  The most common form of URI is the URL
...

—  IRI (Internationalized Resource Identifier)
—  IRI is an extension to URI, URIs are limited to a subset of the
ASCII character set, but IRIs may contain characters from the
Universal Character Set (Unicode/ISO 10646)
On the Semantic Web, IRIs/URIs identify not only Web documents,
but also real-world objects
CO7216 Semantic Web

38  

Introduction  to  
Ontologies  

39  

What is an Ontology?
—  History and Origin
...

— 

— 

The term “Ontology” is a compound word, originated in
Greek, onto (i
...
being or the nature of things
...
e
...

means “nature of existence

—  Definition in the Dictionary (Merriam-Webster)
— 

— 

“A branch of metaphysics concerned with the nature and
relations of being”
“A particular theory about the nature of being or the kinds of
existents (the kind of things that exists) ”

40

What is an Ontology?
Computer Science Definition  
 

—  An ontology is an engineering artifact [Guarino98]:
—  most prevalent use in AI
—  constituted by a specific shared vocabulary used to
describe a certain reality, plus
—  a set of explicit assumptions regarding the intended
meaning of the vocabulary
...

—  objects or entities that are assumed to exist in the domain
of interest
—  relationships that hold between them(roles)
formally, where D is a domain and R is a set of
relevant relations on D
CO7216 Semantic Web

42  

What is an Ontology?
“An  ontology  is  a  formal  specification  of  a  
conceptualization”    
                                                                                       –      Thomas  Gruber  
Describes

Specified  by
Ontology

Concepts

Domain
Modelled  by  

CO7216 Semantic Web

43  

Conceptualization
—  ‘‘An ontology is language dependent while a

conceptualisation is language independent ’’
English:  Cat  

Deutsch:  Katze  

中文：猫  

Arabic    ‫سنور قط‬

Translating the terms in the ontology from one language to the other
(e
...
English to French) does not change the ontology conceptually
 
CO7216 Semantic Web

44  

Ontological Commitment
—  Ontology of a shared domain can be described by defining a set of
— 
— 
— 
— 
— 
— 

representational terms
...
g
...
 
Domain  independent    
 
Top-­‐level    
Ontology  

Domain  
Ontology  

Task  
Ontology  

Application  
Ontology  

CO7216 Semantic Web

Generic  task  
e
...
 Stock  trading  
Online  payment  

Concepts  corresponding  to  
roles  played  by  domain  
entities  while  performing  
certain  tasks  or  activities    
 
46  

Structure of an Ontology
An ontology consists of a finite lists of terms and
relationships between those terms
...


CO7216 Semantic Web

47  

Classes and their hierarchies

sub  class  of  

“University”  domain    
Person  

Student  

Staff  

Academic  
Staff  

Technical  
Staff  

Admin  
Staff  

Postgraduate  

CO7216 Semantic Web

Undergraduate  

48  

Relationships (Some examples)

Gavin  

Tom  

is  a  

is  a  

Admin  
Staff  

Postgraduate  
Student  

friendOf  
Gavin  

Tom  

hasEmail  
Tom  

t123@student
...
ac
...
g
...
g
...
g
...
g
...
g
...
g
...
g
...
g
...

CO7216 Semantic Web

53  

https://www
...
org/wiki/Lists_of_ontologies  

Some Well-known Ontologies
—  Dublin Core (Document publishing)
—  Gene Ontology (Bioinformatics)
—  WordNet (Lexical Database)
—  CIDOC CRM (Culture & Heritage)
—  FOAF (Friend-Of-A-Friend)
—  Geopolitical ontology
—  VCard RDF (business card)
—  Pizza Ontology (an useful example comes with

Protégé editor)  
     …
...

—  RDF Schema: Vocabulary description language for
describing properties and classes of RDF resources
...
OIL stands
for Ontology Inference Layer (superseded by OWL )
—  OWL: a richer language for describing classes and am
expressive suite of relationships between classes
...

—  Provides formal language for expressing knowledge
...

—  For example:
—  OWL is an ontology language and W3C standard –
Based on Description Logic
...
eatOnly(veg) -> vegetarian(X)

—  If X and Y are sibling, Z is the father of Y then Z is the father of X
— 

sibling(X,Y) father(Z,Y) -> father(Z,X)

—  And
—  John is a Professor
— 

Prof(John)

—  John eat meats
...
eatSome(meat)

—  Alice’s biological father is John, Tom is Alice’s brother
— 

father(John, Alice) brother(Tom, Alice)
CO7216 Semantic Web

59  

Logical reasoning: example
—  We can deduce
—  John is a faculty
— 

faculty(John)

—  John is also a member of Staff
—  Staff(John)

Description  Logic    
reasoning  

—  John is a non-vegetarian
— 

non-vegetarian(John)

—  John is Tom’s father
— 

father(John, Tom)

Deductive  rule-­‐based  
reasoning  

We’ll  get  back  to  this  later  when  studying  
reasoning  over  OWL  ontologies!!  
CO7216 Semantic Web

60  

Logic: advantage
—  Logic is used to uncover ontological knowledge which is

implicitly given
...


CO7216 Semantic Web

61  

Open World Assumption (OWA)
Yi  eats  
chicken  tikka  

Open World Assumption
Knowledge is incomplete, hence we have
to admit undefined answers

boiled  rice  
potato  salads    
tofu  
Alessandro    
eats  
 pasta  
boiled  rice  
potato  salads    

Vegetarian?

Yi

Alessandro

Closed world
assumption

No

Yes

Open world
assumption

No

???

hash  browns  

CO7216 Semantic Web

62  

Summary: Features of the Semantic Web
—  AAA - Anyone can say Anything about Any topic
...

—  Open world/close world: there is always more information
that could be known
...

—  The network effect: The value of joining in increases with
the number of people who have joined
...

—  Semantic Web endeavors to describe data on the web in
a “meaningful” way to make it suitable for processing by
machines
...


CO7216 Semantic Web

64  

Acknowledgements
     Lecture  Notes  based  on  slides  provided  by  
     Monika  Solanki      (Leicester)    
 
       Some  slides  inspired  from:    
       Ian  Horrocks  (University  of  Oxford)  and  his  working  group    
 
     The  intelligent  agent  image  was  inspired  from  a  slide  by    
     Charlie  Abela  (University  of  Malta)    

CO7216 Semantic Web

65  



---

Title: Semantic web Lecture Notes
Description: Univeristy of Leicester- Semantic web lectures notes and past exams papers with answers.

Buy These NotesPreview