02 - semantic web technologien - uri and rdf

Semantic Web Technologies

LectureDr. Harald Sack

Hasso-Plattner-Institut für IT Systems EngineeringUniversity of Potsdam

Winter Semester 2012/13

Lecture Blog: http://semweb2013.blogspot.com/This file is licensed under the Creative Commons Attribution-NonCommercial 3.0 (CC BY-NC 3.0)

Dienstag, 23. Oktober 12

http://semweb2013.blogspot.com


http://creativecommons.org/licenses/by-nc/3.0/

http://creativecommons.org/licenses/by-nc/3.0/

Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam

2 1. Introduction 2. Semantic Web - Basic Architecture

Languages of the Semantic Web - Part 1

3. Knowledge Representation and LogicsLanguages of the Semantic Web - Part 2

4. Applications in the ,Web of Data‘

Semantic Web Technologies Content



3

2. Semantic Web - Basic ArchitectureLanguages of the Semantic Web - Part 1



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2. Semantic Web Basic ArchitectureThe Languages of the Semantic Web - Part 1

• Uniform Resource Identifier - URI• Recapitulation: XML and XMLSchema• Resource Description Framework - RDF

• RDF Schema• How Do We Get Semantics into WWW?

• µFormats, schema.org, RDFa and GRDDL• Query Language SPARQL• Why RDF(S) is not enough



5

What is this?



6

What`s the difference?



7

Semiotic Triangle

Symbol Objectstands for

Ogden, Richards, Semiotic Triangle, 1923

„apple“

symbolizes refers to

Concept

shared concept



8

Uniform

Resource

Identifier

□ different types of resource identifiers all constructed according to a uniform schema

□ whatever may be identified via URI

□ to distinguish one resource from another

The Designator in the Web



9

Uniform Resource Identifier ■ A Uniform Resource Identifier (URI) defines a simple and extensible schema

for worldwide unique identification of abstract or physical resources (RFC 3986).

■ Resource can be every object with a clear identity (according to the context of the application) □ as e.g., web pages, books, locations, persons, relations among

objects, abstract concepts, etc.■ The concept of URI is already established in various domains, as e.g., □ the Web (URL, PRN, pURL), □ Books and publications (ISBN, ISSN), □ Digital Object Identifier (DOI)


http://www.ietf.org/rfc/rfc3986.txt

http://www.ietf.org/rfc/rfc3986.txt

URI, Resource and Representation


10

http://www.tour-eiffel.fr/index.htmlURI

Eiffel Tower

Resource

Metadata: Content-type: text/htmlData:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Le site officiel de la Tour Eiffel</title> ...</html>

representation

identifies

represents (stands for)


http://www.tour-eiffel.fr/index.html


















Representation and Presentation


11Metadata: Content-type: text/htmlData:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Le site officiel de la Tour Eiffel</title> ...</html>

Representation

defines

Presentation





















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HTTP Request / Response

User clicks

Browser sendsHTTP Request

GET http://www.tour-eiffel.fr/index.html HTTP/1.1Host: www.tour-eiffel.frAccept: text/html





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Browser sends HTTP RequestGET http://www.tour-eiffel.fr/index.html HTTP/1.1Host: www.tour-eiffel.frAccept: text/html

Web Server ofwww.tour-eiffel.fr

Web Server processes request

Web Server sends HTTP ResponseHTTP/1.1 200 OKContent-Length: 3134Content-Type: text/html; charset=utf-8

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Le site officiel de la Tour Eiffel</title> ...</html>

Browser interprets representation and displays presentation

HTTP Request / Response




http://www.tour-eiffel.fr

http://www.tour-eiffel.fr















Designator and Designatum


14

The web page describes (designates) the Eiffel Tower

≠

Designator

Designatum

The Eiffel Tower is described (designated) by the web page



15

2. Semantic Web Basisarchitektur2.1 Uniform Resource Identifier - URI

Bezeichner und Bezeichnetes

René Magritte: La trahison des images (1928)


http://en.wikipedia.org/wiki/The_Treachery_of_Images

http://en.wikipedia.org/wiki/The_Treachery_of_Images


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Designator and Designatum

17

W3C: Architecture of the World Wide Web, Volume One

□A resource can be described (designated) via Metadata □ Even if the resource itself cannot be delivered from the

web server, probably its representation might be available that describes the resource sufficiently.

The distinguishing characteristic of [information] resources is that all of their essential characteristics can be conveyed in a message.



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Metadata



Metadaten

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Metadata

• „Metadata are data that contain information about other data“ and „Metadata are required to fulfill a specific purpose or to achieve a specific result“(informal definition, Wikipedia)

• „Metadata are structures, encoded data that describe the characteristics of information bearing entities for the purpose of identification, retrieval, evaluation and administration of the described entities.“(W. R. Durrell: Data Administration: A practical Guide to Data Administration. McGraw – Hill, 1985)

• „Metadata is machine understandable information about web resources or other things“ (Tim Berners-Lee: Axioms of Web Architecture: Metadata, 1997)



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URI, Ressource and Metadata

http://www.tour-eiffel.fr/index.htmlURI

Information about the Eiffel Tower

Resource:Eiffel Tower Metadata

Metadata: Content-type: text/htmlData:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Le site officiel de la Tour Eiffel</title> ...</html>

Representation

identifies

represents

describes

Resource:Eiffel Tower

(stands for)

(designates)






















Address


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Uniform Resource Identifier

Name

■ URI combines□ Address (Locator)

□ Uniform Resource Locator (URL, RFC 1738)□ denotes, where a resource can be found in the Web by stating its

primary access mechanism□ might change during life cycle

□ Identity (Name)

□ Uniform Resource Name (URN, RFC 2141)□ persistent identifier for a Web resource□ remains unchanged during life cycle



22 ■ US-ASCII Encoding■ Percent Encoding for reserved characters, or characters that do not exist in US-ASCII

encoding existieren pct-encoded = "%" HEXDIG HEXDIG

■ Reserved characters with special function reserved = gen-delims / sub-delims gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@“ sub-delims = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="

■ Permitted characters unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"

■ Extension to Universal Character Code (Unicode/ISO 10646)□ Internationalized Resource Identifier (IRI, RFC 3987)

e.g.:

URI - Generic Syntax



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URI = schema"://"[userinfo"@"]host[:port][path]["?"query]["#"fragment]

■ schema: e.g. http, ftp, mailto,...■ userinfo: e.g. username:password■ host: e.g. Domain-Name, IPv4/IPv6 Address■ port: e.g. :80 for standard http port■ path: e.g. path in file system of WWW server■ query: e.g. parameters to be passed over to applications■ fragment: e.g. determines a specific fragment of a document




24 Media Fragment Identifier■ Multimedia Data cover temporal and spatial dimension■ pinpoint acces to multimedia resources via URI Media Fragment Identifier

(W3C Media Fragments URI 1.0, 25. September 2012, W3C Recommendation)■ Example:

■ WWW Client and WWW Server have to take care for handling media fragments correctly, i.e. consequences for http protocol

http://www.example.com/example.ogg#track=‘audio‘http://www.example.com/example.ogg#track=‘audio‘&t=10s,20shttp://www.example.com/example.ogg#track=‘video‘&xywh=160,120,320,240




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■ What if a URI for a resource does not exist?■ Define a URI by yourself:□ avoid overlaps

use your own website □ enables documentation at the same place

( Content Negotiation)■ Separate URI for resource (Designatum) and its documentation (Designator)

via URI references (i.e. via "#" fragments) or Content Negotiation

z.B.: http://hpi.uni-potsdam.de/harald_foaf.rdf#me

URIs im Semantic Web

Sauermann, Cyganiak: Cool URIs for the Semantic Web, W3C Interest Group Note 03 December 2008, http://www.w3.org/TR/cooluris/


http://hpi.ui-potsdam.de/harald_foaf.rdf#

http://hpi.ui-potsdam.de/harald_foaf.rdf#

http://www.w3.org/TR/cooluris/

http://www.w3.org/TR/cooluris/


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27




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To a computer, then, the web is a flat, boring world devoid of meaning. This is a pity, as in fact documents on the web describe real objects and imaginary concepts, and give particular relationships between them. For example, a document might describe a person. The title document to a house describes a house and also the ownership relation with a person. [...]

Tim Berners-Lee: W3 future directions, Plenary at 1st WWW Conference, 1994, Geneva (Switzerland)



■How do I represent:

„Harald Sack has the phone number ++49 (331) 5509-527“

<phonenr> <owner>Harald Sack</owner> <number>++49 (331) 5509-527</number></phonenr>

<person name=“Harald Sack“> <phonenr>49 (331) 5509-527</phonenr></person>

<person name=“Harald Sack“ phone=“49 (331) 5509-527“ />

is there a unique (intuitive) way to model knowledge?

Knowledge Representation... a simple example



Harald Sack

has the phone number

++49 (331) 5509-527



„Harald Sack has the phone number ++49 (331) 5509-527“



Harald Sackhas phone number

++49 (331) 5509-527



„Harald Sack has the phone number ++49 (331) 5509-527“■ Intuitive knowledge representation with directed graphs



Knowledge Representation and Communication

Conceptual Domain ModelObjects and Relations

<xsd:schema xmlns:xsd="http://..."><xsd:annotation> Schema A</xsd:...</xsd:schema> XML Schema

is translated into

Senderuses schema A

Receiveruses schema A

XML-based communicationvia schema A

XML-Parser

Deployment


■Problem: new communication partners will not understand


Senderuses schema A

Receiveruses schema A

XML-based communicationvia schema A

XML-Parser

???

new communication partneruses Schema B

???

new communication partner uses Schema C

???




■Schemata have to be translated

Reengineering ofconceptual model

Matching

XML DocumentTranslation

Generation (XSLT)

XML DocumentTranslation

Schemata A <-> B

<xsd:schema xmlns:xsd="http://..."><xsd:annotation> A-Schema</xsd:...</xsd:schema>

<xsd:schema xmlns:xsd="http://..."><xsd:annotation> B-Schema</xsd:...</xsd:schema>

Schema A Schema B

<xsl:stylesheet version="1.0”xmlns:xsl="http://....Transform"<xsl:template match="/">....</xsl:template></xsl:stylesheet>

<xsl:stylesheet version="1.0”xmlns:xsl="http://....Transform"<xsl:template match="/">....</xsl:template></xsl:stylesheet>




■Schemata have to be translated■Problems:□Reengineering is expensive and complicated□Reengineering would not be necessary with a conceptual knowledge

representation languagh□Schema translations (XSLT) are expensive and not necessary

use abstract level above XML

Resource Description Framework (RDF)• simple and extensible




Level 1(Objekte)

XMLXMLSchema

Level 3(abgeschlossene

Welten)

OWL

RDFRDFSchema

Level 2(Wissen über

Objekte)




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RDF



39

Resource■ can be everything (in principle)...■must be uniquely identified and be referencable■ ...simply via URI

Resource Description Framework



40


Description■ = Descriptions of resources■ ...via representing their relationships among each other■ ...relationships can be represented as graphs



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Framework■ = Combination of web based protocols (URI, HTTP, XML,...)■ based on formal model (semantics)■ defines all allowed relationships among resources



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■Originally developed to define metadata for web resources ■ 1995-1997: proprietary Meta Content Framework (Netscape)■ 1997 RDF as general description language for metadata, W3C Draft■ 1998 first RDF W3C recommendation (http://www.w3c.org/RDF)

■Definition of an XML subset (machine readable) with predefined (fixed) semantics (machine understandable)

■ Simple, universal semantic data model■ RDF enables high interoperability



43


Harald Sack

has phone number

++49 (331) 5509-527

Subject

Property

Object



44


Harald Sack

has phone number

++49 (331) 5509-527

■ Knowledge in RDF is expressed as a list of statements■ all RDF statements follow the same simple schema



45


Harald Sack

has phone number

++49 (331) 5509-527

Subject

Property

Object



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• Resources:Objects that can be addressed via URI

• Properties:Attributes for the description of resources

• Statements (RDF-Triple):Resource + Property + Object / Value

URI URI URI / Literal


Constituents of the RDF-Graphen• URI:

• to reference resources uniquely


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http://hpi-web.de/HaraldSack http://swt1213.blogspot.com/

http://hpi-web.de/Personal#writesBlog

S

P

O


http://swt1213.blogspot.co


http://hpi-web.de/Personal#


Constituents of the RDF-Graphen• Literals:

• describe data values that do not have a separate existence• strings, interpretation via datatype


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http://hpi-web.de/HaraldSack ++49-331-5509-527

http://hpi-web.de/Personal#hasPhoneNumber

S

P

O




Constituents of the RDF-Graphen• Literals:

• typed literals can be expressed via XML Schema datatypes• Namespace for typed literals: http://www.w3.org/2001/XMLSchema#

• Example: “Semantics“^^<http://www.w3.org/2001/XMLSchema#string>

• Language Tags denote the (natural) language of the text:• Example: “Semantik“@de , “Semantics“@en


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http://www.w3c.org/2001/xml-schema#

http://www.w3c.org/2001/xml-schema#

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

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

Constituents of the RDF-Graphen• Blank Nodes:

• Denotes existence of an individual with specific attributes, but without providing an identification or reference


50


S

htttp://www.hpi-web.de/personal#person

rfds:typeP

O


http://www.hpi-web.de/Perspnal#

http://www.hpi-web.de/Perspnal#

RDF Representations• Node-Edge-Node Triple


51


http://hpi-web.de/HaraldSack

http://hpi-web.de/Personal#writesBlog

S

P

O

http://swt1213.blogspot.com/






RDF Representations• N3 Notation

•Simple listing of triples• { http://hpi-web.de/HaraldSack, http://hpi-web.de/Personal#writesBlog, http://swt1213.blogspot.com/ }


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http://hpi-web.de/Personal#hatBlog

http://hpi-web.de/Personal#hatBlog

http://sewe0910.blogspot.com


RDF Representations• Turtle (Terse RDF Tripel Language)• Extension of N3• URIs in angle brackets• Literals in quotation marks• Triple ends with a period• Whitespaces will be ignored


53


<Subject> <Property> <Object> .<Subject> <Property> “Object“ .


RDF Representations• Turtle (Terse RDF Tripel Language)


54


<http://hpi-web.de/HaraldSack> <http://hpi-web.de/Personal#writesBlog> <http://swt1213.blogspot.com/>.

<http://hpi-web.de/HaraldSack> <http://hpi-web.de/Personal#hasPhoneNumber> “++49-331-5509-527“.








RDF Representations• Turtle (Terse RDF Tripel Language)


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@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .@prefix dc: <http://purl.org/dc/elements/1.1/> .@prefix ex: <http://example.org/stuff/1.0/> .

<http://www.w3.org/TR/rdf-syntax-grammar> dc:title "RDF/XML Syntax Specification (Revised)"@en ; ex:editor [ ex:fullname "Dave Beckett"^^xsd:string ; ex:homePage <http://purl.org/net/dajobe/> ] .


http://www.w3.org/1999/02/22-rdf-syntax-ns#


http://purl.org/dc/elements/1.1/


http://example.org/stuff/1.0/

http://example.org/stuff/1.0/

http://www.w3.org/TR/rdf-syntax-grammar

http://www.w3.org/TR/rdf-syntax-grammar

http://purl.org/net/dajobe/

http://purl.org/net/dajobe/

RDF Representations• RDF XML-Serialization


56


<xml version=“1.0“ encoding=“utf-8“><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#“ xmlns:pers=“http://hpi-web.de/Personal#“>

<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:hasPhoneNr>++49-331-5509-527</pers:hasPhoneNumber> </rdf:Description>

<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:writesBlog> <rdf:Description rdf:about=“http://swt1213.blogspot.com/“></rdf:Description> </pers:writesBlog> </rdf:Description></rdf:RDF>


http://sw0910.blogspot.com



57


hasPhoneNumber


http://swt1213.blogspot.com/writesBlog

Resource

Literal


<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:hasPhoneNumber>++49-331-5509-527</pers:hasPhoneNumber> <rdf:Description>

<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:writesBlog rdf:resource=“http://swt1213.blogspot.com/“ /> </rdf:Description></rdf:RDF>

Resource

++49-331-5509-527









<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:hasPhoneNumber>++49-331-5509-527</pers:hasPhoneNumber> <rdf:Description>

<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“> <pers:writesBlog rdf:resource=“http://swt1213.blogspot.com/“ /> </rdf:Description></rdf:RDF>


58



Resource

Literal

Resource

++49-331-5509-527hasPhoneNumber








59



Resource

Literal

Resource

++49-331-5509-527


<rdf:Description rdf:about=“http://hpi-web.de/HaraldSack“ pers:hasPhoneNumber=“++49-331-5509-527“> <pers:writesBlog rdf:resource=“http://swt1213.blogspot.com/“/> </rdf:Description></rdf:RDF>

hasPhoneNumber
















60


http://hpi-web.de/Dozenten#HaraldSack

Resource

Literal

Resource

++49-331-5509-527

<xml version=“1.0“ encoding=“utf-8“><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#“ xmlns:pers=“http://hpi-web.de/Personal#“

xml:base=“http://hpi-web.de/Dozenten“>

<rdf:Description rdf:about=“#HaraldSack“ pers:hasPhoneNumber=“++49-331-5509-527“> <pers:writesBlog rdf:resource=“http://swt1213.blogspot.com/“/> </rdf:Description></rdf:RDF>

hasPhoneNumber










61



Resource

Literal

Resource

++49-331-5509-527

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix pers: <http://hpi-web.de/Personal#> .@base <http://hpi-web.de/Dozenten> .

:HaraldSack pers:hasphoneNumber “++49-331-5509-527“ .:HaraldSack pers:writesBlog <http://swt1213.blogspot.com/> .

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix pers: <http://hpi-web.de/Personal#> .@base <http://hpi-web.de/Dozenten> .

:HaraldSack pers:hasPhoneNumber “++49-331-5509-527“ ; pers:writesBlog <http://swt1213.blogspot.com/> .

Short Cut

hasPhoneNumber









http://hpi-web.de

http://hpi-web.de







http://hpi-web.de

http://hpi-web.de





http://wwwsoup.blogspot.com

http://wwwsoup.blogspot.com




62



Resource

Literal

Resource

++49-331-5509-527

<xml version=“1.0“ encoding=“utf-8“><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#“ xmlns:pers=“http://hpi-web.de/Personal#“ xml:base=“http://hpi-web.de/Dozenten“

<rdf:Description rdf:ID=“HaraldSack“ pers:hasPhoneNumber=“++49-331-5509-527“> <pers:writesBlog rdf:resource=“http://swt1213.blogspot.com/“/> </rdf:Description></rdf:RDF> Datei http://hpi-web.de/Dozenten.rdf

hasPhoneNumber





http://hpi-web.de/Dozent#

http://hpi-web.de/Dozent#







@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix pers: <http://hpi-web.de/Personal#> .

:HaraldSack pers:hasPhoneNumber “++49-31-5509-527“ ; pers:writesBlog <http://swt1213.blogspot.com/> .


63



Resource

Literal

Resource

++49-331-5509-527

Datei http://hpi-web.de/Dozenten.rdf

hasPhoneNumber
















64


http://hpi-web.de/ws1213#swt


http://hpi-web.de/Lecture#Name

http://hpi-web.de/Lecture#SWS

4

<xml version=“1.0“ encoding=“utf-8“><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#“ xmlns:lv=“http://hpi-web.de/Lecture#“ >

<rdf:Description rdf:about=“http://hpi-web.de/ws1213#swt“> <lv:Name rdf:datatype=“http://www.w3c.org/2001/XMLSchema#string“> Semantic Web Technologies </lv:Name> <lv:SWS rdf:datatype= “http://www.w3c.org/2001/XMLSchema#integer“> 4 </lv:SWS> </rdf:Description></rdf:RDF>




http://hpi-web.de/LehrVeranstaltung#


http://hpi-web.de/Lecture#

http://hpi-web.de/Lecture#

http://hpi-web.de/ws0910#

http://hpi-web.de/ws0910#

http://www.w3c.org/2001/XMLSchema#

http://www.w3c.org/2001/XMLSchema#


65



Semantic Web Technologieshttp://hpi-web.de/Lecture#Name

http://hpi-web.de/Lecture#SWS4

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix lv: <http://hpi-web.de/Lecture#> .

<http://hpi.web.de/ws1213#swt> lv:Name “Semantic Web Technologies“^^<http://www.w3c.org/2001/XMLSchema#string> ; lv:SWS “4“^^<http://www.w3c.org/2001/XMLSchema#integer> .

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix lv: <http://hpi-web.de/Lecture#> .

<http://hpi.web.de/ws1213#swt> lv:Name “Semantic Web Technologies“; lv:SWS 4 . Abgekürzte

Schreibweise



















66


Multi Valued Relations and Blank Nodes• Example: • A lecture takes place twice a week in two different rooms• How to model this in RDF?

Problem: not unique


http://hpi-web.de/Lecture#hasName

http://hpi-web.de/Lecture#hasRoom

http://hpi-web.de/Lecture#hasDate

HS3

Die 13.30-15.00

http://hpi-web.de/Lecture#hasRoom

http://hpi-web.de/Lecture#hasDate

H-1.52

Mi 13.30-15.00







http://hpi-web.de/WS0809/semanticweb



67


Multi Valued Relations and Blank Nodes• Example: • A lecture takes place twice a week in two different rooms• How to model this in RDF?

hpi-lv:hasRoom


Semantic Web Technologieshpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

H-1.52

Mi 13.30-15.00

hpi-lv:hasRoom

hpi-lv:hasDate

hpi-lv:takesPlace

hpi-lv:takesPlace





68


Blank Nodes• Blank Nodes (Bnodes) can be introduced to represend multi valued

relationships• Blank Nodes can be introduced for resources that don‘t need a name

(auxiliary nodes)

hpi-lv:hasRoom



hpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

hpi-lv:takesPlace





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Anonymous Blank Nodes

hpi-lv:hasRoom



hpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

hpi-lv:takesPlace

<xml version=“1.0“ encoding=“utf-8“><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#“ xmlns:hpi-lv=“http://hpi-web.de/Lecture#“ >

<rdf:Description rdf:about=“http://hpi-web.de/ws1213#swt“> <hpi-lv:takesPlace rdf:parseType=“Resource“/> <hpi-lv:hasDate>Die, 13.30-15.00</hpi-lv:hasDate> <hpi-lv:hasRoom>HS3</hpi-lv:hasRoom> </hpi-lv:takesPlace> </rdf:Description>









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Anonymous Blank Nodes

hpi-lv:hasRoom



hpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

hpi-lv:takesPlace

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix hpi-lv: <http://hpi-web.de/Lecture#> .

<http://hpi-web.de/ws1213#swt> hpi-lv:takesPlace [ hpi-lv:hasDate “Die 13.30-15.00“; hpi-lv:hasRoom “HS3“ ] .








http://hpi-web.de/

http://hpi-web.de/


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Dereferencable Blank Nodes

hpi-lv:hasRoom



hpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

ID1

hpi-lv:takesPlace

<rdf:Description rdf:about=“http://hpi-web.de/ws1213#swt“> <hpi-lv:takesPlace rdf:nodeID=“ID1“/> <rdf:Description>

<rdf:Description rdf:nodeID=“ID1“> <hpi-lv:hasDate>Die 13.30-15.00</hpi-lv:hasDate> <hi-lv:hasRoom>HS3<hpi-lv:hasRoom> </rdf:Description></rdf:RDF>





72


Dereferencable Blank Nodes

hpi-lv:hasRoom



hpi-lv:hasName

HS3

Die 13.30-15.00

hpi-lv:hasDate

ID1

hpi-lv:takesPlace

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix hpi-lv: <http://hpi-web.de/Lecture#> .

<http://hpi-web.de/ws1213#swt> hpi-lv:takesPlace _:ID1 .

_:ID1 hpi-lv:hasDate “Die 13.30-15.00“; hpi-lv:hasRoom “HS3“ .








http://hpi-web.de/

http://hpi-web.de/


73


Lists• General Data structure to enumerate any resoures or literals• Only shortcuts, no additional semantic expressivity

• Distinguish between• Container

open list, i.e. extension (new entries) possible• Collections

closed list, i.e. no extension possible



74


RDF Container

rdf:type

rdf:Seq

hpi-lv:hasParticipants

http://hpi-web.de/SchmidtJoseph

http://hpi-web.de/SchulzeEgon

http://hpi-web.de/MuellerFranz

http://hpi-web.de/BurgerAntonrdf:_1


rdf:_2

rdf:_3

rdf:_4

@prefix hpi-lv: <http://hpi-web.de/Lecture#> .@prefix rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns#> .


http://hpi-web.de/semanticweb/







75


RDF Container


<rdf:Description rdf:about=“http://hpi-web.de/ws1213#swt“> <lv:hasParticipants> <rdf:Seq> <rdf:li rdf:resource=“http://hpi-web.de/BurgerAnton“ /> <rdf:li rdf:resource=“http://hpi-web.de/MuellerFranz“ /> <rdf:li rdf:resource=“http://hpi-web.de/SchmidtJoseph“ /> <rdf:li rdf:resource=“http://hpi-web.de/SchulzeEgon“ /> </rdf:Seq> </lv:hasParticipants> </rdf:Description>







http://hpi-web.de/semanticweb


RDF-Container• the root node of the container is

assigned a container-typ via rdf:type• rdf:Bag

unordered set of elements,there is no given order of elements

• rdf:Seqordered set of elements,

• rdf:Altdefines alternatives of elements only one element of the given alternatives is relevant for the application


76




77


RDF Container

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix lv: <http://hpi-web.de/Lecture#> .@base <http://hpi-web.de/>

:swt lv:hasParticipants [ a rdf:Seq; rdf:_1 <BurgerAnton>; rdf:_2 <MuellerFranz>; rdf:_3 <SchmidtJoseph>; rdf:_4 <SchulzeEgon> . ] .






http://hpi-web.de/

http://hpi-web.de/

RDF-Collection


78


rdf:nil

lv:hasParticipants rdf:first

rdf:rest

http://hpi-web.de/SchmidtJoseph

http://hpi-web.de/SchulzeEgon


http://hpi-web.de/BurgerAnton

List is splitted recursively in Head (first) and Tail (rest).


rdf:rest

rdf:rest

rdf:rest

rdf:first

rdf:first

rdf:first











RDF-Collection

<rdf:Description rdf:about=“http://hpi-web.de/ws1213#swt“> <lv:hasParticipant rdf:parseType=“Collection“> <rdf:Description rdf:about=“http://hpi-web.de/BurgerAnton“ /> <rdf:Description rdf:about=“http://hpi-web.de/MuellerFranz“ /> <rdf:Description rdf:about=“http://hpi-web.de/SchmidtJoseph“ /> <rdf:Description rdf:rabout=“http://hpi-web.de/SchulzeEgon“ /> </lv:hasParticipant> </rdf:Description>


79





RDF-Collection


80


:swt lv:hasParticipant [ rdf:first <BurgerAnton>; rdf:rest [ rdf:first <MuellerFranz>; rdf:rest [ rdf:first <SchmidtJoseph>; rdf:rest [ rdf:first <SchulzeEgon>; rdf:rest rdf:nil .] ] ] ] .







http://hpi-web.de/

http://hpi-web.de/

RDF-Collection


81


:swt lv:hasParticipant ( <BurgerAnton> <MuellerFranz> <SchmidtJoseph> <SchulzeEgon>) .







http://hpi-web.de/

http://hpi-web.de/


82

What can we model with RDF?



83


„My dear Watson,...I suppose that the Gardenerhas killed the Butler!“



84


RDF-Reification• RDF permits interleaving of statements,

i.e. to make statements about statements• Example:

„My dear Watson,...I suppose that the Gardenerhas killed the Butler!“



85


RDF-Reification• RDF permits interleaving of statements, i.e. to make statements about

statements• Example:• Sherlock Holmes supposes that the Gardener has killed the Butler

•Part 1: The Gardener has killed the Butler

•Part 2: Sherlock Holmes supposes

exv:Gardener exv:hasKilled exv:Butler .

exv:SherlockHolmes exv:supposes ???? .



86


RDF-Reification• rdf:Statement

defines an RDF Statement, consisting of Subject, Predicate and Object• rdf:subject - the described resource

• rdf:predicate - the original property

• rdf:object - the value of the property

<rdf:Description rdf:about=“http://example.org/StatementOnGaertner“> <rdf:subject rdf:resource=“http://example.org/Gardener“ /> <rdf:predicate rdf:resource=“http://example.org/Crime#hasKilled“ /> <rdf:object rdf:resource=“http://example.org/Butler“ /> <rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement" /></rdf:Description>


http://example.org/#

http://example.org/#


87


RDF-Reification

<rdf:Description rdf:about=“http://example.org/StatementOnGardener“> <rdf:subject rdf:resource=“http://example.org/Gardener“ /> <rdf:predicate rdf:resource=“http://example.org/Crime#hasKilled“ /> <rdf:object rdf:resource=“http://example.org/Butler“ /> <rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement" /></rdf:Description>

<rdf:Description rdf:about=“http://example.org/SherlockHolmes“> <exv:supposes rdf:resource=“http://example.org/StatementOnGaertner“ /> </rdf:Description>

SherlockHolmes

exv:supposes

StatementOnGardener

Gardener

exv:hasKilled

Butler

rdf:subject

rdf:predicate

rdf:object


http://example.org/StatementOnGaertner


http://example.org/Gaertner

http://example.org/Gaertner

http://example.org/#hatErmordet

http://example.org/#hatErmordet

http://example.org/Butler

http://example.org/Butler

http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement

http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement

http://example.org/SherlockHolmes

http://example.org/SherlockHolmes




88


RDF-Reification

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@exv <http://example.org/Crime#>

<SherlockHolmes> exv:supposes <StatementOnGardener> .<StatementOnGardener> a rdf:Statement ; rdf:subject <Gardener> ; rdf:predicate exv:hasKilled ; rdf:object <Butler> .

SherlockHolmes

exv:supposes

StatementOnGardener

Gardener

exv:hasKilled

Butler

rdf:subject

rdf:predicate

rdf:object




http://example.org

http://example.org


89


RDF-Reification• Is Reification really necessary?• Modeling data provenance • Formalizing statements about Reliability (Trust) • Definition of Metadata about Statements (Assertions, Statements)

• for (general) knowledge representation (Ontologie Construction):• Transformation of Relations into Classes



90

RDF and Data Integration



91

• Simple Example: Bibliography Database

ID Author Title Publisher Year

ISBN 0-00-651409-X HS-123 WWW S-001 2004

ID Name Homepage

HS-123 Harald Sack http://hpi-web.de/HaraldSack.html

ID Publisher Location

S-001 Springer Heidelberg



http://hpi-web.de/HaraldSack.html



92

ISBN 0-00-651409-X

WWW

2004

a:title

a:year

Springer

Heidelberg

a:publishername

a:publisherlocation

a:publisher

Harald Sack


a:authorname

a:authorhomepage

a:author

• Database export into a set of relations






93

ISBN 0-00-651409-X

u:author

Harald Sack

u:name

http://.../paper

u:cites

Very important paper

u:title


ISBN 0-00-651409-X

WWW

2004

a:title

a:year

Springer

Heidelberg

a:publishername

a:publisherlocation

a:publisher

Harald Sack


a:authorname

a:authorhomepage

a:author





94

ISBN 0-00-651409-X

WWW

2004

Springer

Heidelberg

Harald Sack


ISBN 0-00-651409-X

u:author

Harald Sack

u:name

http://.../paper

u:cites


u:title

a:title

a:year

a:publishername

a:publisherlocation

a:publisher

a:authorname

a:authorhomepage

a:author






95

WWW

2004

Springer

Heidelberg

Harald Sack


u:author

Harald Sack

u:name

http://.../paper

u:cites


ISBN 0-00-651409-X

u:title

a:title

a:year

a:publishername

a:publisherlocationa:publisher

a:authorname

a:authorhomepage

a:author






96

RDF - a Resume

RDF Model -- Summary• An RDF Model is a set of RDF statements• Statement := (subject, property, object)• Subject is a resource• Property is a resource• Object is ether a resource or a literal



97








98

SO ... WE NEED A WAY TO DEFINE RDF SCHEMATA FORCLASSES AND RELATIONS ?!

Next lecture

RDFS



99

Bibliography

• Ch. Meinel, H. Sack: WWW - Kommunikation, Internetworking, Webtechnologien, Springer, 2004.

• D. R. Hofstadter: Gödel, Escher, Bach - ein endlos geflochtenes Band, Dtv, 1992.

2. Semantic Web Basic Architecture2.1 Uniform Resource Identifier2.2 XML und XMLSchema2.3 Resource Description Framework


http://www.amazon.de/gp/product/3540442766/ref=as_li_ss_tl?ie=UTF8&tag=moresemantic-21&linkCode=as2&camp=1638&creative=19454&creativeASIN=3540442766





100

Bibliography

• P. Hitzler, S. Roschke, Y. Sure: Semantic Web Grundlagen, Springer, 2007.

• P. Hitzler, M. Krötzsch, S. Rudolph:Foundations of Semantic Web Technologies,CRC Press, 2009.





http://www.amazon.de/gp/product/142009050X/ref=as_li_ss_tl?ie=UTF8&tag=moresemantic-21&linkCode=as2&camp=1638&creative=19454&creativeASIN=142009050X

http://www.amazon.de/gp/product/142009050X/ref=as_li_ss_tl?ie=UTF8&tag=moresemantic-21&linkCode=as2&camp=1638&creative=19454&creativeASIN=142009050X

Lecture Semantic Web Technologies, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam

101

□Bloghttp://semweb2013.blogspot.com/

□Webseitehttp://www.hpi.uni-potsdam.de/studium/lehrangebot/itse/veranstaltung/semantic_web_technologien-3.html

□bibsonomy - Bookmarkshttp://www.bibsonomy.org/user/lysander07/swt1213_02





http://www.hpi.uni-potsdam.de/studium/lehrangebot/itse/veranstaltung/semantic_web_technologien-3.html






http://www.bibsonomy.org/user/lysander07/swt1213_02




02 - semantic web technologien - uri and rdf

Education

phone number

semantic web

dews1213swt

basic architecture

universitt

rdf rdf schema

semantic web

swt lv