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Cover page images (keys)

Questions (and Answers) on the Semantic Web

Munchen, Germany, 7 October 2005

Ivan Herman, W3C

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Slides of the presentation held at the Semantic Web Days, on the 7th of October 2005, in Munich, Germany. The event is coordinated by the European Networks of Excellence REWERSE (Reasoning on the Web with Rules and Semantics) and Knowledge Web (Realizing the Semantic Web).

You Know Everything On Semantic Web Already, So…


Well, Let Me Help You…

Some questions come up regularly, so I collected them…

  1. Is the Semantic Web AI on the Web?
  2. Isn’t the RDF Model (and RDF/XML) way too complex?
  3. Where is the “Web” in SW?
  4. Why should I use RDF?
  5. What are these OWL layers?
  6. Why “OWL” and not “WOL”?
  7. Must I use OWL for my vocabularies?
  8. How do I extract triplets from and RDF Graph?
  9. Isn't This Research Only?
  10. Are we done?

Is the Semantic Web AI on the Web?

Picture of a hype article with a text on it saying 'Beware of the Hype'

The Semantic Web is not AI…

Some things may come to the SW

But AI is more…

Isn’t the RDF Model (and RDF/XML) way too complex?

(just look at RDF/XML…)

RDF is a graph!

A Simple RDF Example

A small RDF graph with three statements, followed by an RDF/XML encoding thereof

RDF/XML has its Problems

Other Encoding Examples…

    :subject :pred_1 [:pred_2 :object_1; :pred_3 :object_2; ]
        <subject uri="..."/>
        <predicate uri="..."/>
        <object>A Literal</object>
    Class(animationEntity complete 
        unionOf(animate animateMotion …)

Where is the “Web” in SW?

The “Web” is in the URI-s!


What Merge Can Do...

resource for the conference
like before + resources for myself and massimo linked to the conference like before + resource for W3C, team and a reference to me like before + resource for alumni and a reference to massimo like before + two links labelled 'knows' connecting massimo and me

Another Web Aspect: Open vs. Closed Worlds

Why should I use RDF?

(Couldn’t I simply use XML with XML Schema instead?)

(or: Couldn’t I simply use a relational database instead?)

It Depends…

RDF’s Force is its Flexibility

Finding New Relationships

But... RDF Does Not Make XML Obsolete!

What are these OWL layers?


OWL Full

Example for a Possible Problem (in OWL Full)

<owl:Class rdf:ID="A">
      <owl:onProperty rdf:resource=".../22-rdf-syntax-ns#type"/>
      <owl:allValueFrom rdf:about="#B"/>
<owl:class rdf:ID="B">
  <owl:complementOf rdf:parseType="Collection">
    <owl:Class rdf:about="#A"/>
<owl:Thing rdf:ID="C">
  <rdf:type rdf:resource="#A"/>

OWL Description Logic (DL)

Goal: maximal subset of OWL Full against which current research can assure that a decidable reasoning procedure is realizable

OWL Lite

“Description Logic”

Note on OWL layers

Why “OWL” and not “WOL”?

Why “OWL” and not “WOL”?

The drawing of Winnie the Pooh and OWL

Where does the metadata and ontologies come from?

(Should we really expect the author to type in all this metadata?)

It May Be Around Already…

RDF Can Also Be Generated

Formalizing the Scraper Approach: GRDDL

<html xmlns="">
  <head profile="">
    <title>Some Document</title>
    <link rel="transformation"
       href="" />
    <meta name="DC.Subject" content="Some subject"/>      
<rdf:Description rdf:about="">
  <dc:subject>Some subject</dc:subject>

Another Future Solution: XHTML2

<span property="dc:date">March 23, 2004</span>
  <span property="dc:title">High-tech rollers hit casino for £1.3m</span>
  By <span property="dc:creator">Steve Bird</span> …	
<rdf:Description rdf:about="">
  <dc:date>March 23, 2004</dc:date>
  <dc:title>High-tech rollers hit casino for £1.3m</dc:title>
  <dc:creator>Steve Bird</dc:creator>

And for Ontologies?

There are Already Ontologies Around…

Must I use OWL for my vocabularies?

Must I use OWL for my vocabularies?

Simple Knowledge Organisation System (SKOS)

Example: Entries in a Glossary (1)

“(i) Any expression which is claimed to be true. (ii) The act of claiming something to be true.”
“A general concept, category or classification. Something used primarily to classify or categorize other things.”
“(i) An entity; anything in the universe. (ii) As a class name: the class of everything; the most inclusive category possible.”

(from the RDF Semantics Glossary)

Example: Entries in a Glossary (2)

A slide a simple SKOS glossary

Example: Entries in a Glossary (3)

A slide a simple SKOS glossary

Example: Taxonomy (1)

Illustrates “broader” and “narrower”

  • Travelling
  • Politics
  • RDF
    • OWL

(From MortenF’s weblog categories. Note that the categorization is arbitrary!)

Example: Taxonomy (2)

A slide a simple SKOS glossary

Example: Thesaurus (1)

Economic cooperation
Used For
Economic co-operation
Broader terms
Economic policy
Narrower terms
Economic integration, European economic cooperation, European industrial cooperation, Industrial cooperation
Related terms
Scope Note
Includes cooperative measures in banking, trade, industry etc., between and among countries

(from UK Archival Thesaurus)

Example: Thesaurus (2)

A slide a simple SKOS glossary

SKOS Core Overview

Complementarity of SKOS and OWL (Why Having SKOS?)

“Core” Vocabularies

How do I extract triplets from and RDF Graph?

Querying RDF Graphs

Simple SPARQL Example

SELECT ?cat ?val
WHERE { ?x rdf:value ?val. ?x category ?cat }
A simple RDF Graph, with some matching patterns highlighted

Other SPARQL Features

SPARQL Usage in Practice

Why Yet Another W3C Query Language?

Isn't This Research Only?

(or: does this have any industrial relevance whatsoever?)

Not Any More…

Lots of Tools

Data integration examples

MuseoSuomi Application dump


Vodaphone screen dump

Baby CareLink

Baby care link application dump

Are we done?

Not Yet…


W3C’s Rules Workshop

Current Plans

Lots of Theoretical Questions to Solve

The traditional layercake model of SW The two tower lternative for the SW architecture (with Rules and Ontologies side by side)

Beyond Rules: Trust

A Number of Other Issues…

Thank You!

These slides (with links)
Mail me:

Now For Real…

Other Questions?