This document discusses semantic search using the semantic web. It begins by describing limitations of current keyword-based search engines. It then introduces the semantic web, which aims to represent information in a way that is understandable by machines through standards like XML, RDF, RDFS, and OWL. This will allow semantic search engines to better understand the meaning of web pages to improve search results. Examples are provided of representing information about a conference using these semantic web standards to illustrate how machines could infer new facts not explicitly stated.

1. Semantic Search
with
Semantic Web
Presented by:
Zahra Sadeghi
1

2. keyword-based search engines
• the quality of the search results:
– It often happens that relevant pages are not indexed by a
traditional search engine
• very time-consuming task for the users who have to perform
it manually.
– the result of a search engine is a single web page, and to retrieve
information it is necessary to perform several queries.
• semantically similar queries can return different results
• very closely related to the spelling of the word and not to its
meaning
• important information can be reached only if its specific
internet address is known.
2

3. The Original Web
• 1989: Web was “invented” by Tim Berners-Lee
3
Web of relationships amongst named objects

4. Where we are Today
4

5. What is the Problem?
• Consider a typical web page:
•The current Web represents information using:
- natural language ( English,…)
-graphics, multimedia
•Humans can process this easily
• can deduce facts from partial information
5
• Semantic content is accessible to
humans but not (easily) to
computers…

6. What information can we see…
• WWW2002
• The eleventh international world wide web conference
• Sheraton waikiki hotel
• Honolulu, hawaii, USA
• 7-11 may 2002
• 1 location 5 days learn interact
• Registered participants coming from
• australia, canada, chile denmark, france, germany, ghana, hong kong,
india, ireland, italy, japan, malta, new zealand, the netherlands, norway,
singapore, switzerland, the united kingdom, the united states, vietnam,
zaire
• Register now
• On the 7th May Honolulu will provide the backdrop of the eleventh
international world wide web conference. This prestigious event …
• Speakers confirmed
• Tim berners-lee
• Tim is the well known inventor of the Web, …
• Ian Foster
• Ian is the pioneer of the Grid, the next generation internet …
6

7. What information can a machine
see…
WWW2002
The eleventh inteqnational woqld wide web
confeqence
Sheqaton waikiki hotel
Honolulu, hawaii, USA
7-11 may 2002
1 location 5 days leaqn inteqact
Registeqed paqticipants coming fqom
austqalia, canada, chile denmaqk, fqance,
geqmany, ghana, hong kong, india,
iqeland, italy, japan, malta, new zealand,
the netheqlands, noqway, singapoqe,
switzeqland, the united kingdom, the united
states, vietnam, zaiqe
Registeq now
On the 7th May Honolulu will pqovide the
backdqop of the eleventh inteqnational woqld
wide web confeqence. This pqestigious event 
Speakeqs confiqmed
Tim beqneqs-lee
Tim is the well known inventoq of the Web, 
Ian Fosteq
Ian is the pioneeq of the Gqid, the next
geneqation inteqnet 
7

8. The current Web =
the second Web generation
• The first generation Web started with handwritten HTML
pages;
• The second generation made the step to machine generated
and often active HTML pages.
• They were meant for direct human processing (reading,
browsing, form-filling).
• The current web=syntactic web
– A place where computers do the presentation (easy) and
people do the linking and interpreting (hard).
• The third generation Web= "Semantic Web",
– aims at machine processable information. 8

9. Why semantic web?
• The fact that accurate Natural Language
Processing (NLP) is not yet achievable in
general domains, has led to numerous efforts
– to create standardized semantic languages
for the web.
• The semantic web aims
– to create content which both humans and
machines can understand
9

10. The main intent of the Semantic
Web
• to give machines much better access to information
resources
• to improve the existing web with a semantic layer
that allows machines to understand it
• to enable software programs to process information
efficiently
• Moving from a Web of "finding things" to a Web of
"doing things"
10

11. solution=XML?
• HTML :
• a markup language for a specific kind of hypertext documents.
• Is not extensiable
• XML :
• a markup language for arbitrary document structure,
• Simplifies the process of defining and using metadata.
• Is a meta language: provides a basic structure and a set of rules
for developing other languages.
• An XML document consists of a properly nested set of open
and close tags, where each tag can have a number of
attribute-value pairs. 11

12. solution=XML?
12

13. XML document = labelled tree
why not use XML to represent semantics?
13

14. Solution:
XML markup with “meaningful” tags?
<name>WWW2002
The eleventh inteqnational woqld wide webcon</name>
<location>Sheqaton waikiki hotel
Honolulu, hawaii, USA</location>
<date>7-11 may 2002</date>
<slogan>1 location 5 days leaqn inteqact</slogan>
<participants>Registeqed paqticipants coming fqom
austqalia, canada, chile denmaqk, fqance,
geqmany, ghana, hong kong, india, iqeland,
italy, japan, malta, new zealand, the
netheqlands, noqway, singapoqe, switzeqland,
the united kingdom, the united states,
vietnam, zaiqe</participants>
<introduction>Registeq now
On the 7th May Honolulu will pqovide the
backdqop of the eleventh inteqnational woqld
wide web confeqence. This pqestigious event 
Speakeqs confiqmed</introduction>
<speaker>Tim beqneqs-lee</speaker>
<bio>Tim is the well known inventoq of the
Web,</bio>…
14

15. Still the Machine only sees…
<name>WWW2002
The eleventh inteqnational woqld wide webc</name>
<location>Sheqaton waikiki hotel
Honolulu, hawaii, USA</location>
<date>7-11 may 2002</date>
<slogan>1 location 5 days leaqn inteqact</slogan>
<paqticipants>Registeqed paqticipants coming fqom
austqalia, canada, chile denmaqk, fqance, g
eqmany, ghana, hong kong, india, iqeland,
italy, japan, malta, new zealand, the net
heqlands, noqway, singapoqe, switzeqland, the
united kingdom, the united states, vietnam,
zaiqe</paqticipants>
<intqoduction>Registeq now
On the 7th May Honolulu will pqovide the backdq
op of the eleventh inteqnational woqld wide w
eb confeqence. This pqestigious event 
Speakeqs confiqmed</intqoduction>
<speakeq>Tim beqneqs-lee</speakeq>
<bio>Tim is the well known inventoq of the W</bio>
<speakeq>Ian Fosteq</speakeq>
<bio>Ian is the pioneeq of the Gqid, the ne</bio>
15

16. Disadvantages of XML
• XML tags can add meaning to data
• Understanding the tags is only meaningful to humans.
• does not impose any common interpretation of the
data contained in the document.
• XML is aiming at the structure of documents
• XML just describes grammars
•the vocabulary of the tags and their allowed
combinations is not fixed
16

17. "The author of the page is Ora".
<document href="page">
<author>Ora</author>
</document>
<document>
<details>
<uri>href="page"</uri>
<author>
<name>Ora</name>
</author>
</details> </document>
<document>
<author>
<uri>href="page"</uri>
<details>
<name>Ora</name>
</details>
</author> </document>
<document href="http://www.w3.org/test/page" author="Ora" />
17

18. The complexity of querying the
XML tree
• the query you write has to be independent
of the choice of them.
• Must convert the set of all possible
representations of a fact into one statement
• A standard ways of writing statements… ?
RDF
The same RDF tree results from many XML trees.
18

19. RDF
Resource Description Framework
• a language used for representing
information about resources on the
web.
• a basic ontology language.
• Motivation:
• to provide a standard for meta-data,
for descriptions about resources on
the web.
19

20. The basic construction in RDF
• an object-attribute-value triple:
• an object O has an attribute A with value V.
• commonly written as A(O,V)
• A subject, predicate and object triple
• Resource, Property, and Property value triple
• Resource = anything that can have a URI, such as
• "http://www.w3schools.com/RDF"
• Property = a Resource that has a name, such as
• "author" or "homepage"
• Property value = the value of a Property, such as
• "Jan Egil " or "http://www.w3schools.com"
• (note that a property value can be another resource)20

21. RDF Statements example
• a Resource, a Property, and a Property value
=
a subject, predicate and object
• "The author of http://www.w3schools.com/RDF is
Jan Egil Refsnes".
• The subject ?
http://www.w3schools.com/RDF
• The predicate?
author
• The object ?
Jan Egil Refsnes
22

22. 23

23. RDF Syntax
• RDF has an XML syntax that has a specific meaning:
• Every Description element describes a resource
• Every attribute or nested element inside a Description is a property
of that Resource
• We can refer to resources by using URIs
<Description about="some.uri/person/ian_horrocks">
<hasColleague resource="some.uri/person/uli_sattler"/>
</Description>
<Description about="some.uri/person/uli_sattler">
<hasHomePage>http://www.cs.mam.ac.uk/~sattler</hasHomePage>
</Description>
<Description about="some.uri/person/carole_goble">
<hasColleague resource="some.uri/person/uli_sattler"/>
</Description>
24

24. RDF Schema=RDFS
• an object-oriented modelling language
• RDF :provides a model for describing information
• The semantics (meaning of the informations) is described
using RDFS.
• RDF Schema „semantically extends‟ RDF to enable us
– to talk about classes of resources, and the properties that
will be used with them.
– It allows you to define classes
– It allows you to define relationships between classes
– It allows you to define properties of classes
• RDFS = RDF Vocabulary Definition Language
25

25. RDFS Example
• There is a relationship between Stream and BodyOfWater
• The relationship is called emptiesInto
26
WATERSOURCE
Stream
River
Creek
BodyOfWater
Lake
sea

26. <rdfs:Class rdf:ID="WaterSource" />
<rdfs:Class rdf:ID="Stream">
<rdfs:subClassOf rdf:resource="#WaterSource"/>
</rdfs:Class>
<rdfs:Class rdf:ID="BodyOfWater">
<rdfs:subClassOf rdf:resource="#WaterSource"/>
</rdfs:Class>
27

27. <rdfs:Class rdf:ID="River">
<rdfs:subClassOf rdf:resource="#Stream"/>
</rdfs:Class>
<rdfs:Class rdf:ID="Lake">
<rdfs:subClassOf rdf:resource="#BodyOfWater"/>
</rdfs:Class>
...
<rdf:Property rdf:ID="emptiesInto">
<rdfs:range rdf:resource="# BodyOfWater"/>
<rdfs:domain rdf:resource="#River"/>
</rdf:Property>
28

28. • Basically, we describe now real Web resources according to the
developed schema
• ...
• <River rdf:ID="Yangtze"
• <emptiesInto
• rdf:resource="EastChinaSea"/>
• </River>
• ...
29

29. What are the advantages of
applying RDF Schema
• Inference!
• We can infer new facts from already existing facts
• River is a subclass of Stream !
• Yangtze is a stream
• Stream is a subclass of WaterSource !
• Yangtze is a WaterSource
• River emptiesInto BodyOfWater !
• Yangtze (stream) empties Into EastChinaSea
• EastChinaSea is a BodyOfWater
30

30. OWL
Web Ontology Language
• Latest standard (February 2004) in ontology languages
• OWL is an ontology language
• primarily designed to describe and define classes.
• Classes are therefore the basic building blocks of an OWL ontology.
• Built on top of RDF (OWL semantically extends RDF(S)),
• OWL is for processing information on the web
• OWL was designed to be interpreted by computers
• OWL was not designed for being read by people
• OWL is written in XML
• OWL has three sublanguages
31

31. Ontology
• Borrowed from philosophy : the study of “The nature of
being”
• the exact description of things and their relationships.
• Describes a list of terms and the relations between them
• a "representation of a shared conceptualization of a
particular domain".
• have been developed in Artificial Intelligence to facilitate
knowledge sharing and reuse.
• For the web: the exact description of web information
and relationships between web information.
• in the context of the Semantic Web: is a document or file
that formally defines the relations among terms
32

32. An example
• Class_def Animal
class_def Plant
subclass_of Not Animal
class-def tree
subclass_of Plant
class_def branch
slot_constraint is-part_of
has_value tree
34

33. the use of ontologies
• e-commerce sites
– to enable machine-based communication
between buyer and seller,
• in search engines.
– By using ontologies the search engines can
escape from the current keyword-based
approach,
– can find pages that contain syntactically
different, but semantically similar words
35

34. Agents
• They need to recognize, interpret, and respond to
communication acts from other agents.
• They must communicate and understand meaning.
• They must advertise their capabilities, and recognize the
capabilities of other agents.
• They must locate meaningful information resources on
the Web and combine them
• suppose Agent 1 sends a message to Agent 2 and in this
message is a pointer to Agent 1‟s ontology.
• Agent 2 can then look in Agent 1's ontology to see what
the terms mean
36

35. Semantic search
• Conventional Web expanded into a Semantic
Web
• At the moment semantic search engines only
exist for specialized areas of knowledge
• Shall use conceptual representation of Web
pages
• Search engines in future should „understand‟
meaning of Web pages far enough to enable
„sensible‟ queries 37

36. An example
• An agent is searching for information about
mechanical devices, as defined in a public
ontology (SHO).
• A document contains the term “FUEL
PUMP” which the agent has never
encountered.
38

37. 39

38. • Swoogle : a system that automatically discovers
SWDs(online documents written in RDF and OWL) using
RDF and OWL.
• Developed by the university of Baltimore County
• human users are expected to be semantic web researchers
• Helps users integrate semantic web data distributed on the
web.
• Facilates the finding of appropriate ontologies 40

39. References
• The Semantic Web - on the respective Roles of XML and
RDF,Stefan Decker1, Frank van Harmelen3,4, Jeen
Broekstra4 Michael Erdmann5, Dieter Fensel3, Ian Horrocks
2, Michel Klein3, Sergey Melnik
• Semantic Web and RDF,Introduction,Denis Helic
• An Introduction to RDF(S) and a QuickTour of OWL,the
university of Manchester
• Where are the Semantics in the Semantic Web?, Michael
Uschold
• An Introduction to the Semantic Web, Considerations for
building multilingual Semantic Web sites and
applications,Jeremy J. Carroll
• Facilitating Semantic Web Search with Embedded Grammar
Tags,Gautham K.Dorai and Yaser Yacoob
41