Key ingredients of the Semantic Web explained in 30 minutes.:
1. WHAT IS THE GOAL?
2. WHAT ARE THE BUILDING BLOCKS?
3. HOW DO WE CREATE THE GRAPH? WHY LINKED DATA?
4. SHORT INTRODUCTION TO ONTOLOGIE�S
4. VISION FOR THE WEB
TIM BERNERS-LEE,THE 1ST WORLD WIDE WEB
CONFERENCE, GENEVA, MAY 1994:
DESCRIBE DOCUMENTS IN MACHINE READIBLE FORM
CREATE MEANINGFUL LINKS (“RELATIONSHIPVALUES”)
“ONLY WHEN WE HAVETHIS EXTRA LEVEL OF SEMANTICS
WILL WE BE ABLETO USE COMPUTER POWERTO HELP
US EXPLOITTHE INFORMATIONTO A GREATER EXTENT
THAN OUR OWN READING.”
5. Aims of the Semantic Web
BRIDGINGTHE GAP BETWEEN A WEB OF
DOCUMENTSTO A WEB OF DATA,WITH
TYPED OBJECTS ANDTYPED RELATIONSHIPS
ADDING MACHINE-READABLE METADATA
TO EXISTING CONTENT, SOTHAT
INFORMATION CAN BE PARSED, QUERIED,
REUSED
6. Aims of the Semantic Web
DEFINING SHARED SEMANTICS FORTHIS
METADATATO ALLOW INTEROPERABILITY
BETWEEN APPLICATIONS AND FOR
ADVANCED PURPOSES, SUCH AS REASONING
ENABLING MACHINE-READABLE KNOWLEDGE
AT WEB SCALE, MAKING INFORMATION MORE
EASYTO FIND AND PROCESS
7. The Semantic Web, circa 2010
MOST STANDARDISATION WORK IS DONE IN
THE W3C:
HTTP://WWW.W3.ORG/
INCUBATOR GROUPS,WORKING GROUP,
INTEREST GROUPS:
WGS FOR SPARQL, RDB2RDF, RIF, ETC.
HCLS IG, SOCIAL WEB XG, ETC.
9. Identifying resources with URIs
URIS ARE USEDTO IDENTIFY EVERYTHING IN A
UNIQUE AND NON-AMBIGUOUS WAY
NOT ONLY PAGES (AS ONTHE CURRENT WEB),
BUT ANY RESOURCE (PEOPLE, DOCUMENTS,
BOOKS, INTERESTS, ETC.)
A URI FOR A PERSON IS DIFFERENT FROM A URI
FOR A DOCUMENT ABOUTTHE PERSON,
BECAUSE A PERSON IS NOT A DOCUMENT!
e.g. http://deri.ie/user/maciej-dabrowski
e.g. http://deri.ie/content/modelling-preference-relaxation-e-commerce
10. Defining assertions with RDF
• URIS IDENTIFY RESOURCES:
• WE USE RDF (RESOURCE DESCRIPTION
FRAMEWORK)TO DEFINE ASSERTIONS
ABOUTTHESE RESOURCES
• RDF IS A DATA MODEL;A DIRECTED, LABELED
GRAPH USING URIS
• RDF IS BASED ONTRIPLES:
– <SUBJECT> <PREDICATE> <OBJECT>.!
13. Abbreviating uris
PREFIX ex: http://example.org/#
ex:maciej = <http://example.org/#maciej>
ex:maciej-dabrowski
ex:MDabrowski-lecture3
ex:author
ex:Semantic_Web
Introduction to the
Semantic Web
ex:title
ex:subject
14. Reuse existing vocabularies
PREFIX dct: http://purl.org/dc/terms/
http://deri.ie/user/maciej-dabrowski
http://example.org/MDabrowski-lecture3
dct:creator
http://dbpedia.org/resource/Semantic_Web
Introduction to the
Semantic Web
dct:title
dct:subject
15. RDF by example
!
!
@prefix dct: <http://purl.org/dc/terms/> . !
<http://example.org/dm110-semweb>!
!dct:title “Introduction to the Semantic Web” ; !
!dct:author <http://www.deri.ie/users/maciej-dabrowski> ; !!
!dct:subject <http://dbpedia.org/resource/Semantic_Web> .!
16. RDFA
A WAY OF EMBEDDING RDF IN (X)HTML
DOCUMENTS:
ONE PAGE FOR BOTH HUMANS AND
MACHINES
DON’T NEEDTO REPEATYOURSELF
INTRODUCING NEW XHTML ATTRIBUTES
CURRENT WORK IS ONGOING ON RDFa 1.1:
FOR PROFILES, ETC.
20. Defining semantics with ontologies
• RDF PROVIDES A WAYTO WRITE ASSERTIONS
ABOUT URIS
• WHAT ABOUTTHE SEMANTICS OFTHESE
ASSERTIONS, E.G.TO STATETHAT HTTP://
XMLNS.COM/FOAF/0.1/KNOWS IDENTIFIES AN
ACQUAINTANCE RELATIONSHIP?
• ONTOLOGIES PROVIDE COMMON
SEMANTICS FOR RESOURCES ONTHE
SEMANTIC WEB
21. Ontologies consist mainly of classes and
properties
– :Person a rdfs:Class .!
– :father a rdfs:Property .!
– :father rdfs:domain :Person .!
– :father rdfs:range :Person .!
:Maciej
:Mark
:father
:Person
a
:Person
a