03 Semantic Web Technologies - RDFS and RDFa

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, 30. 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

RDF

Semantic Web Technologies Last Lecture....



3 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



4

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

RDFS



5


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



6

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



7

Why RDFSchema...?

• An application program can define and use RDF data• ….if the application program knows, which terms and classes to use, as e.g.

•name, title, year, … •name, blog, phone number…•author, cites, …

• But.....• Are all terms known?• Are all terms correct?• Are there (logical) relations among the terms?

• We need a language for data definition: RDF Schema

• officially called “RDF Vocabulary Description Language”



8

• First W3C draft in April 1998, W3C Recommendation Feb. 2004.

• RDF Schema defines a data model for the creation of RDF statements• abstract data type (class)• hierarchical class model and class inheritance (subclasses)• Syntax for common data exchange

• = „Language for the definition of structured vocabularies.“

RDFSchema



9

• RDFSchema allows:• Definition of classes

•Class instantiation in RDF via <rdf:type>• Definition of properties and restrictions • Definition of hierarchies

•Subclasses and superclasses

RDFSchema



10

exv:isManagedByexv:SemanticWebTechnologies exv:HaraldSack

Lecture

Staff

Prof. Senior Researcher

Person

Course

Seminar

is managed by

domainrange

subClassOf

subClassOf

subClassOfsubClassOf

class

classclass class

classproperty

class

class

subClassOf

rdf:type rdf:typeRDF

RDFS

Example


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


http://hpi-web.de/HaraldSack



11

•Classes• rdfs:Resource

every entity of an RDF model is instance of this class• rdf:Property

Base class for properties• rdfs:Class

Concept of a class, defines an abstract object and is applied (with rdf:type)to create instances

• rdfs:Literal Class for literals

• and additionallyrdfs:Datatype, rdf:XMLLiteral, rdfs:Container, rdfs:ContainerMembershipProperty

Vocabulary



12

•Properties• rdfs:subClassOf

transitive property to define inheritance hierarchies for classes • rdfs:subPropertyOf

transitive property to define inheritance hierarchies for properties• rdfs:domain

defines the domain of a property concerning a class• rdfs:range

defines range of a property concerning a class

Vocabulary



13 ■Properties□ rdfs:subClassOf

transitive property to define inheritance hierarchies for classes

(1)

(2)

(3)

Vocabulary



1415 ■Properties□ rdfs:subPropertyOf

transitive property to define inheritance hierarchies for properties

(1)

(2)

(3)

Vocabulary



s – subclass relationt – instance relation

rdfs:Resourcerdfs:Class

t

ts

rdfs:Literal

t s

rdf:Property

t s

rdfs:range rdfs:domain

tt

rdfs:subClassOf

t rdfs:comment

t

rdf:typet

rdfs:subPropertyOf

t

Language Model



16

• Further Properties• rdfs:seeAlso

defines a relation of a resource to another, which explains it

• rdfs:isDefinedBysubproperty of rdf:seeAlso, defines the relation of a resource to its definition

• rdfs:commentcomment, usually as text

• rdfs:label „readable“ name of a resource (contrary to ID)

Vocabulary



17

exv:isManagedByexv:SemanticWebTechnologies exv:HaraldSack

Lecture

Staff

Prof. Senior Researcher

Person

Course

Seminar

is managed by

domainrange

subClassOf

subClassOf

subClassOfsubClassOf

class

classclass class

classproperty

class

class

subClassOf

rdf:type rdf:type RDF

RDFS

RDF(S) Knowledge Base

A-BoxAssertional Knowledge

T-BoxTerminologcal Knowledge







@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.@base <http://hpi-web.de/ws1213>

:Course a rdfs:Class .:Lecture a rdfs:Class; rdfs:subClassOf :Course.:Seminar a rdfs:Class ; rdfs:subClassOf :Course.

:Person a rdfs:Class .:Staff a rdfs:Class ; rdfs:subClassOf :Person .:SeniorResearcher a rdfs:Class ; rdfs:subClassOf :Staff .

:isManagedBy a rdf:Property; rdfs:domain :Course ; rdfs:range :Staff .

:SemanticWebTechnologies a :Lecture .:HaraldSack a :SeniorResearcher .:SemanticWebTechnologies :isManagedBy :HaraldSack .

Turtle

Example


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


http://www.w3.org/2000/01/rdf-schema#

http://www.w3.org/2000/01/rdf-schema#

http://www.w3.org/2001/XMLSchema#

http://www.w3.org/2001/XMLSchema#

http://hpi-web.de/WS0910#

http://hpi-web.de/WS0910#


• RDFSchema defines a data model for the definition of simple ontologies (knowledge representations).

• Via RDFSchema ontologies RDF statements (facts) can be expressed

• More than XML:• (small) ontological agreement about modelling primitives• Possibility to define own vocabularies

• Next steps:• more logic• Constrains, dependencies, and rules

Summary



How much knowledge

(semantics) has RDF(S)



How much knowledge (semantics) has RDF(S)

exv:SemanticWebTechnologies

exv:Lecture

rdf:type

exv:takes Place

exv:hasRoom

HS3

Tue 13.30-15.00

exv:hasDateSemantic Web Technologies

exv:hasName

exv:takesPlace exv:Event

rdf:type

rdfs:Class rdfs:Classrdfs:Property





How much knowledge (semantics) has RDF(S)


exv:Lecture

rdf:type

exv:takes Place

exv:hasRoom

HS3

Tue 13.30-15.00

exv:hasDateSemantic Web Technologies

exv:hasName


rdf:type


• The semantics of a term from an RDF(S) ontology is given in terms of its properties and its values (instances)





What Conclusions can we

deduce with RDF(S)?




exv:Lecture

exv:takes place



rdf:type

• Deduction of entity class membership from the domain of one of its properties

What conclusions can we deduce with RDF(S)?




exv:Lecture

exv:takes place




• Deduction of entity class membership from the range of one of its properties

rdf:typerdf:type




exv:Lecture

exv:takesPlace


rdfs:Class

rdfs:Classrdfs:Property

rdf:type rdf:type

exv:Course

rdfs:subClassOf

rdfs:Class

• Deduction of entity superclass membership froma class hierarchy.

rdf:type




exv:Alice

exv:Person

exv:isMotherOf

exv:isMotherOf exv:Person

rdfs:Class

rdfs:Property

rdf:typerdf:type

rdfs:Class

exv:isParentOf

rdfs:Property

rdfs:subPropertyOf

exv:Person exv:Person

rdfs:Class

exv:Bob

• Deduction of new facts from subproperty relationships

exv:Aliceexv:isParentOf

exv:Bob












Is RDF(S) sufficient for

Knowledge Representation

in the Semantic Web?



29








30

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



Semantic Annotation in the Web

• RDF/XML can directly be embedded in an HTML document via <head> and <script>

• RFC 3870 defines Mime-Type application/rdf+xml

<head> <title>My Document</title> <script type="application/rdf+xml"> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://www.w3.org/" dc:title="W3C Homepage"/> </rdf:RDF> </script></head>




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


http://www.w3.org

http://www.w3.org


• W3C recommends linking of external RDF documents via HTML <link> element in HTML <head>

• RDF documents can also embedded via <a href=...> and additionalmarkup (e.g. RDF logo) withinin HTML <body>

<link rel="meta" type="application/rdf+xml" href="Meta-Data-for-Web-Page.rdf"/>



• Problem: HTML and RDF data are separate



wep pageHTML

<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#title> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#type> "product" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#url> "http://www.bestbuy.com:80/site/Plan-9-from-Outer-Space---DVD/6429224.p?id=23883&skuId=7167941" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#image> "http://images.bestbuy.com:80/BestBuy_US/images/products/6429/6429224s.jpg" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#site_name> "Best Buy" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.facebook.com/2008/fbmlapp_id> "125188000891129" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#description> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#upc> "025493070026" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> 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<http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/global-min.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/google-min.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/main_icon_sprite-min.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/pdp-min.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/product_image_headers.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/softgoods-icons.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.w3.org/1999/xhtml/vocab#stylesheet> <http://images.bestbuy.com:80/BestBuy_US/store/styles/tabs-min.css> .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.facebook.com/2008/fbmlapp_id> "125188000891129" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.facebook.com/2008/fbmlapp_id> "125188000891129" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#description> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#description> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#image> "http://images.bestbuy.com:80/BestBuy_US/images/products/6429/6429224s.jpg" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> 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.<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://www.facebook.com/2008/fbmlapp_id> "125188000891129" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#description> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#description> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#image> "http://images.bestbuy.com:80/BestBuy_US/images/products/6429/6429224s.jpg" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#image> "http://images.bestbuy.com:80/BestBuy_US/images/products/6429/6429224s.jpg" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#site_name> "Best Buy" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#site_name> "Best Buy" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#title> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#title> "Plan 9 from Outer Space - DVD" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#type> "product" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#type> "product" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#upc> "025493070026" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#upc> "025493070026" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#url> "http://www.bestbuy.com:80/site/Plan-9-from-Outer-Space---DVD/6429224.p?id=23883&skuId=7167941" .<http://www.bestbuy.com/site/Plan+9+from+Outer+Space+-+DVD/7167941.p?id=23883&skuId=7167941&st=plan%209%20from%20outer%20space&lp=6&cp=1> <http://ogp.me/ns#url> "http://www.bestbuy.com:80/site/Plan-9-from-Outer-Space---DVD/6429224.p?id=23883&skuId=7167941" .

RDF dataTurtle






























































• In principle there are three ways to embed structured datawith explicit semantic annotations within HTML documents

• Domain specific microformats

• Generic RDFa and embedded RDF

• HTML5 Microdata including




• Microformats (µformats) emerged about 2005• (X)HTML Markup to express (limited) semantics in an HTML

document• designed to solve simple, specific problems• designed for humans first, machines second• used in web pages to describe a specific type of information,

as e.g. a person, an event, a product, a review, etc.

• Applications can easily extract data from HTML documents

• In general, Microformats use the class attribute in HTML tags (most times <span> or <div> tags)and assign brief and descriptive names to entities and their properties

Microformats



• Microformats reuse of the following (X)HTML tag attributes:•class

•rel

•rev• Predefined standard microformats:

• hCard - personal data (vCard, RFC2426)• hCalender – calendars and events• rel-Tag – tags, keywords, categories• XFN – XHTML friends network• hReview, VoteLinks -- opinions, ratings, and reviews• XOXO – lists and outlines• ...

http://microformats.org/

Microformats




Microformats


• Simple Example: HTML marked up with hCard microformat

<div class="vcard"> <span class="fn">Joe Blow</span> <span class="title">Senior Manager</span> <span class="org">The Example Company</span> <span class="adr"> <span class="street-address">Hauptstr. 123, </span> <span class="postal-code">14482</span> <span class="locality">Potsdam</span> </span> Tel.<span class="tel">604-555-1234</span> <img class="photo" src="www.example.com/JoeBlow.jpg" /></div>


http://www.example.com/bobsmith.jpg

http://www.example.com/bobsmith.jpg


• Microformats reuse existing (X)HTML attributs to encode structured data

• Microformats can easily be transcoded to RDF via XSLT• New microformat vocabularies first must be consolidated by

the community, while always a new XSLT stylesheet has to be developed for extraction

• By using more than one microformat vocabulary in a single (X)HTML document the processing complexity increases rapidly

• Conflicts with used (X)HTML attributes might be possible

Microformats


Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität PotsdamDienstag, 30. Oktober 12


RDFa

•RDFa = RDF in HTML attributes•enables generic RDF annotation in (X)HTML documents by

reusing existing (X)HTML attributes

•RDFa 1.0 based on XHTML (W3C Recommendation 2008)

•RDFa 1.1 based on HTML5 (W3C Recommendation June 2012)

•RDFa Lite 1.1•RDFa 1.1



•RDFa Lite reuses existing HTML attributes•vocab, •typeof, •property, •resource, •prefix

RDFa


http://www.w3.org/TR/rdfa-lite/#vocab--typeof--and-property






http://www.w3.org/TR/rdfa-lite/#resource




http://www.w3.org/TR/rdfa-lite/#prefix





•First we need a vocabulary to talk about things

<p vocab="http://xmlns.com/foaf/0.1/"> My name is Harald Sack and you can give me a ring via 1-800-555-0527.</p>

RDFa


http://xmlns.com/foaf/0.1/



•Then we have to define the type of thing we are talking about

<p vocab="http://xmlns.com/foaf/0.1/" typeof="Person"> My name is Harald Sack and you can give me a ring via 1-800-555-0527.</p>

RDFa





•Now we can define all properties of the thing we are talking about

RDFa Lite

<p vocab="http://xmlns.com/foaf/0.1/" typeof="Person"> My name is <span property="name">Harald Sack</span> and you can give me a ring via <span property="phone">1-800-555-0527</span>. <img property="img" src="http://hpi-web.de/images/harald.jpg" /></p>




http://manu.sporny.org/images/manu.png


RDFa Lite


•We can create identifiers for the things we are talking about

•resource bezieht sich hier auf Basis-URL der Webseite

<p vocab="http://xmlns.com/foaf/0.1/" resource=“#harald“ typeof="Person"> My name is <span property="name">Harald Sack</span> and you can give me a ring via <span property="phone">1-800-555-0527</span>. <img property="img" src="http://hpi-web.de/images/harald.jpg" /></p>






RDFa Lite


•And if the vocabulary is not sufficient to describe all properties, we can use additional vocabularies by using prefixes

<p vocab="http://xmlns.com/foaf/0.1/" prefix=“ov: http://open.vocab.org/terms/“ resource=“#harald“ typeof="Person"> My name is <span property="name">Harald Sack</span> and you can give me a ring via <span property="phone">1-800-555-0527</span>. My favorite beverage is <span property="ov:preferredBeverage">Green Tea </span>.</p>




http://open.vocab.org/terms/

http://open.vocab.org/terms/

RDFa


•With RDFa you have can add additional functionality•separate content from presentation

<p vocab="http://purl.org/dc/terms/" > <h2 property="title">Syllabus SWT 2012/13</h2> <h3 property="creator" resource="#me">Harald</h3> Creation Date: <span property="created" content="2012-10-28"> 28.10.2012 </span></p>


http://purl.org/dc/terms/


http://purl.org/dc/terms/created


RDFa


•With RDFa you have can add additional functionality•use datatypes from XML Schema Definition

•alternatives:•resource <> about and property <> rel

<p vocab="http://purl.org/dc/terms/" > <h2 property="title">Syllabus SWT 2012/13</h2> <h3 property="creator" resource="#me">Harald</h3> Creation Date: <span property="created" datatype="xsd:gYear"> 2012 </span></p>






RDFa


•Difference between resource and about

•The resource attribute in the <div> element sets the context, i.e. the subject for all subsequent statements.

•Also, when combined with the property attribute, resource can be used to set the object for the statement

<div resource="/alice/posts/trouble_with_bob"> <h2 property="title">The trouble with Bob</h2> <h3 property="creator" resource="#me">Alice</h3> ...</div>


RDFa



•...works, but its a bit convoluted

<ul resource="/alice/posts/trouble_with_bob"> ... <li resource="/alice/posts/trouble_with_bob"> <span property="title">The trouble with Bob</span> </li> <li resource="/alice/posts/jos_barbecue"> <span property="title">Jo's Barbecue</span> </li> ...</ul>




•not correct; the combination of property and resource would generate a different statement than originally intended.

RDFa

<ul resource="/alice/posts/trouble_with_bob"> ... <li resource="/alice/posts/trouble_with_bob" property="title">The trouble with Bob</li> <li resource="/alice/posts/jos_barbecue" property="title">Jo's Barbecue</li> ...</ul>


RDFa



•about is only used to set the context

<ul resource="/alice/posts/trouble_with_bob"> <li about="/alice/posts/trouble_with_bob" property="title">The trouble with Bob</li> <li about="/alice/posts/jos_barbecue" property="title">Jo's Barbecue</li> ...</li>


RDFa


•Difference between property and rel

•rel never considers the textual content of an element•parser is always looking for a target (object)

<div vocab="http://xmlns.com/foaf/0.1/" resource="#me"> <ul rel="knows"> <li resource="http://example.com/bob/#me" typeof="Person"> <a property="homepage" href="http://example.com/bob/"> <span property="name">Bob</span></a> </li> <li resource="http://example.com/eve/#me" typeof="Person"> <a property="homepage" href="http://example.com/eve/"> <span property="name">Eve</span></a> </li> <li resource="http://example.com/harald/#me" typeof="Person"> <a property="homepage" href="http://example.com/harald/"> <span property="name">Harald</span></a> </li> </ul></div>




http://example.com/bob/#me

http://example.com/bob/#me

http://example.com/bob/

http://example.com/bob/

http://example.com/eve/#me

http://example.com/eve/#me

http://example.com/eve/

http://example.com/eve/

http://example.com/manu/#me

http://example.com/manu/#me

http://example.com/manu/

http://example.com/manu/

RDFa


• Distinguish two different sorts of RDF triples•Triple with resource as object•Triple with literal as object

Subjekt Property Objekt

Object is Literal resource/about propertycontent or #PCDATA

Object is Resource (URI)

resource/about property/relhref or

resource



Differences with RDFa 1.0

<html>

...

<div xmlns:dc="http://purl.org/dc/elements/1.1/"> I'm currently reading

<span about=”urn:ISBN:0-596-00027-8”>

<span property="dc:title">

Programming Perl

</span>

by

<span property="dc:creator">Larry Wall</span>

</span>.</div>...</html>

Namespace

Subject

Property

Object(Literal)


RDFa


<?xml version="1.0" encoding="UTF-8"?> <html xmlns="http://www.w3.org/1999/xhtml" version="XHTML+RDFa 1.0" xml:lang="en"> <head>...</head> <body>...</body> </html></xml>

<!DOCTYPE html><html version="HTML+RDFa 1.1" lang="en" xmlns="http://www.w3.org/1999/xhtml" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" xmlns:cc="http://creativecommons.org/ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:foaf="http://xmlns.com/foaf/0.1/">

HTML5

XHTML


http://www.w3.org/1999/xhtml

http://www.w3.org/1999/xhtml

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

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

http://www.w3.org/2000/01/rdf-schema

http://www.w3.org/2000/01/rdf-schema

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

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

http://creativecommons.org/ns

http://creativecommons.org/ns






RDFa

RDFa is already applied by• Google, Yahoo• Facebook, MySpace,

LinkedIn• Best Buy, Tesco, O’Reilly• SlideShare, Digg• WhiteHouse.gov, Library of

Congress, UK government• Newsweek, BBC• ...



...but how does HTML + RDFa become RDF?

RDFa



•Gleaning

•Resource Descriptions

•from Dialects of Languages

http://www.flickr.com/photos/cho45/1402634073/



•Gleaning Resource Descriptions from Dialects of Languages

• GRDDL provides a simple way to extract RDF from (X)HTML documents

• GRDDL applies transformations (XSLT Stylesheets) to extract •RDFa•Mircoformats•RSS

• from (X)HTML documents




• To extract semantic anotation from a document, GRDDL does1.Detect GRDDL Profile metadata2.Link/Fetch transformation data (Extraktors)3.Apply transformations to convert into RDF




<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head profile="http://www.w3.org/2003/g/data-view"> <link rel="transformation" href="http://ns.inria.fr/grddl/rdfa/2008/09/03/RDFa2RDFXML.xsl"/> </head> ... Title: <span property="dc:title"> Digitale Kommunikation: Vernetzung, Multimedia, Sicherheit </span> Category: <span property="dc:subject">Computer Science</span> ...</html>

GRDDL Profildata (XHTML only)

GRDDL Transformation



http://ns.inria.fr/grddl/rdfa/2008/09/03/RDFa2RDFXML.xsl



<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head profile="http://www.w3.org/2003/g/data-view"> <link rel="transformation" href="http://ns.inria.fr/grddl/rdfa/2008/09/03/RDFa2RDFXML.xsl"/> </head> ... Title: <span property="dc:title"> Digitale Kommunikation: Vernetzung, Multimedia, Sicherheit </span> Category: <span property="dc:subject">Computer Science</span> ...</html>

<rdf:RDF xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">... <rdf:Description rdf:about=""> <dc:title> Digitale Kommunikation: Vernetzung, Multimedia, Sicherheit </dc:title> <dc:subject>Computer Science</dc:subject> </rdf:Description>...</rdf:RDF>










...more RDFa ExtractorsRDFa

http://rdfa.info/play/Dienstag, 30. Oktober 12

http://rdfa.info/play/

http://rdfa.info/play/


•HTML5 Microdata extends microformats and addresses its shortcomings•schema.org is the most prominent microdata vocabulary

HTML5 Microdata



schema.org



schema.org

•Initiative started by Bing, Google, Yahoo! on June 2, 2011.

•Goals: •Semantic markup for web page content based on proprietary

HTML5 microdata schemata

•Search engines, web crawler, and Browser recognize and understand schema.org markup

•small number of formats (extensible)

•RDF mapping available



schema.org and Rich Snippets

• Snippets = The few lines of text that appear under every search result• Designed to give users a sense for what’s on the web page and why

it’s relevant to their query

• If Google understands the content on the web page, it can create “Rich” Snippets• = detailed information intended to help users with specific queries• You can help Google find this relevant information by adding

additional microdata as HTML markup



• Microdata extends microformats and addresses its shortcomings • Microdata annotates the DOM with scoped name/value pairs from

custom vocabularies• centered around custom vocabularies:

anyone can define a microdata vocabulary and start embedding custom properties in their own web pages

• works with name/value pairs: every microdata vocabulary defines a set of named properties

• applies concept of “scoping”: microdata re-use the hierarchical structure of the DOM itself to provide a way to say “all the properties within this element are taken from this vocabulary”

HTML5 Microdata



• HTML5 microdata specification comprises•microdata Vocabularies (http://data-vocabulary.org/)

• Persons, Events, Organisations, Products, Reviews, Breadcrumbs, Ads, agreggated Reviews/Ads

•microdata Global Attributes• itemscope (creates resource)

• itemtype (applied vocabulary)• itemid (identifies resource)

• itemprop (property of a resource)• itemref (references on other resources)

HTML5 Microdata


http://data-vocabulary.org

http://data-vocabulary.org


<section itemscope itemtype="http://data-vocabulary.org/Person"> Hello, my name is <span itemprop="name">John Doe</span>, I am a <span itemprop="title">graduate research assistant</span> at the <span itemprop="affiliation">University of Dreams</span>. My friends call me <span itemprop="nickname">Johnny</span>. You can visit my homepage at <a href="http://www.JohnnyD.com" itemprop="url">www.JohnnyD.com</a>. <section itemprop="address" itemscope itemtype="http://data-vocabulary.org/Address"> I live at <span itemprop="street-address">1234 Peach Drive</span> <span itemprop="locality">Warner Robins</span> , <span itemprop="region">Georgia</span>. </section></section>

http://yovisto.com/labs/swt1112/microdata01.html


http://data-vocabulary.org/Person

http://data-vocabulary.org/Person

http://www.JohnnyD.com




http://data-vocabulary.org/Address

http://data-vocabulary.org/Address




http://www.google.com/webmasters/tools/richsnippets





schema.org

http://schema.org/docs/full.html

movies

people

recipes





schema.org


products

music

events

...





schema.org

•extends microdata vocabulary with proprietary category hierarchies:•Creative works:

•CreativeWork, Book, Movie, MusicRecording, Recipe, TVSeries ...

•Embedded non-text objects: •AudioObject, ImageObject, VideoObject

•Event•Organization•Person•Place, LocalBusiness, Restaurant ...•Product, Offer, AggregateOffer•Review, AggregateRating

•and according properties (relations) with different domain and range

•

http://schema.org/docs/full.htmlDienstag, 30. Oktober 12

http://schema.org/CreativeWork

http://schema.org/CreativeWork

http://schema.org/Book

http://schema.org/Book

http://schema.org/Movie

http://schema.org/Movie

http://schema.org/MusicRecording

http://schema.org/MusicRecording

http://schema.org/Recipe

http://schema.org/Recipe

http://schema.org/TVSeries

http://schema.org/TVSeries

http://schema.org/AudioObject

http://schema.org/AudioObject

http://schema.org/ImageObject

http://schema.org/ImageObject

http://schema.org/VideoObject

http://schema.org/VideoObject

http://schema.org/Event

http://schema.org/Event

http://schema.org/Organization

http://schema.org/Organization

http://schema.org/Person

http://schema.org/Person

http://schema.org/Place

http://schema.org/Place

http://schema.org/LocalBusiness

http://schema.org/LocalBusiness

http://schema.org/Restaurant

http://schema.org/Restaurant

http://schema.org/Product

http://schema.org/Product

http://schema.org/Offer

http://schema.org/Offer

http://schema.org/AggregateOffer


http://schema.org/Review

http://schema.org/Review

http://schema.org/AggregateRating





schema.org

http://schema.org/docs/full.htmlDienstag, 30. Oktober 12




schema.org

vs.

RDFa



schema.org - RDFa Mapping

1.<div vocab="http://schema.org/" typeof="Product">2. <img rel="image" src="dell-30in-lcd.jpg" />3. <span property="name">Dell UltraSharp 30" LCD Monitor</span>

5. <div rel="hasAggregateRating" >6. <div typeof="http://schema.org/AggregateRating">7. <span property="ratingValue">87</span>8. out of <span property="bestRating">100</span>9. based on <span property="ratingCount">24</span> user ratings10. </div>11. </div>

13. <div rel="offers" >14. <div typeof="http://schema.org/AggregateOffer">15. <span property="lowPrice">$1250</span>16. to <span property="highPrice">$1495</span>17. from <span property="offerCount">8</span> sellers18. </div>19. </div>20....21.</div>

http://schema.org/docs/datamodel.htmlhttp://schema.rdfs.org/


http://schema.org

http://schema.org





http://schema.org/docs/datamodel.html

http://schema.org/docs/datamodel.html

http://schema.rdfs.org/

http://schema.rdfs.org/


Microdata Usage

http://tripletalk.wordpress.com/2011/01/25/rdfa-deployment-across-the-web/





82








83

via http://www.snee.com/bobdc.blog/2008/10/learning-more-about-sparql.html

SPARQL



84

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.

2. Semantic Web Basic Architecture2.4 RDF Schema2.5 How Do We Get Semantics into WWW?


http://www.amazon.de/gp/product/3540339930/ref=as_li_ss_tl?ie=UTF8&tag=moresemantic-21&linkCode=as2&camp=1638&creative=19454&creativeASIN=3540339930

http://www.amazon.de/gp/product/3540339930/ref=as_li_ss_tl?ie=UTF8&tag=moresemantic-21&linkCode=as2&camp=1638&creative=19454&creativeASIN=3540339930

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

85

□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_03

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




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






http://www.bibsonomy.org/user/lysander07/swt1213_03




03 Semantic Web Technologies - RDFS and RDFa

Education

Transcript of 03 Semantic Web Technologies - RDFS and RDFa