OWL and Ontologies

#1

RDF

Resource Description Framework
Originally about describing metadata about resources on the web.
Its a graph that describes the relationships between data & objects using URIs.

#2

OWL

Ontology Web Language? Web Ontology Language?
Represents/encodes ontologies.
Describes the relationships between data.
Uses RDF.
An attempt at describing meaning.

#3

Meaning?

Ontologies/RDF only classify data under terms or relationships.
If applications "understand" those meanings...
...but the added bit is...
RDF & OWL have known relationships in the graph (e.g. sub-class, property-of,...).
So applications can make inferences based on those relationships.

#4

RDF Triples

An RDF graph is a set of triples:
- Subject
- Predicate
- Object
Subjects and predicates are identified by URI values.
An Object can be another URI or a value.

#5

RDF Triples - Example Graph

Figure 1. Figure

The triples:

<http://cde.berkeley.edu/people#milowski> <http://cde.berkeley.edu/contact#name> "Alex Milowski" .
<http://cde.berkeley.edu/people#milowski> <http://cde.berkeley.edu/contact#title> "Instructor Lacky" .
<http://cde.berkeley.edu/people#milowski> <http://cde.berkeley.edu/contact#email> "mailto:milowski@sims.berkeley.edu" .
<http://cde.berkeley.edu/people#milowski> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://cde.berkeley.edu/contact#person> .

#6

RDF Example Graph

Figure 2. Figure

#7

RDF Example Inferences

Figure 3. Figure

#8

RDF Example in One RDF/XML Document

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:ex="urn:publicid:IDN+cde.berkeley.edu:rdf:ex" >
<ex:University rdf:about="http://www.berkeley.edu">
 <ex:name>UC Berkeley</ex:name>
 <ex:contains>
 <ex:School rdf:about="http://sims.berkeley.edu">
  <ex:name>SIMS</ex:name>
  <ex:offers>
   <ex:Class rdf:about="http://www.sims.berkeley.edu/academics/courses/is290-8/s04/">
    <ex:name>XML and Related Technologies</ex:name>
    <ex:student>Jane Smith</ex:student>
    <ex:student>John Doe</ex:student>
   </ex:Class>
  </ex:offers>
 </ex:School>
 </ex:contains>
</ex:University>
<ex:Instructor rdf:about="http://www.milowski.com">
 <ex:name>Alex Milowski</ex:name>
 <ex:teaches rdf:resource="http://www.sims.berkeley.edu/academics/courses/is290-8/s04/"/>
</ex:Instructor>
</rdf:RDF>

#9

RDF Example in Two RDF/XML Document

First document about the university:

<ex:University rdf:about="http://www.berkeley.edu" 
               xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
 <ex:name>UC Berkeley</ex:name>
 <ex:contains>
 <ex:School rdf:about="http://sims.berkeley.edu">
  <ex:name>SIMS</ex:name>
  <ex:offers>
   <ex:Class rdf:about="http://www.sims.berkeley.edu/academics/courses/is290-8/s04/">
    <ex:name>XML and Related Technologies</ex:name>
    <ex:student>Jane Smith</ex:student>
    <ex:student>John Doe</ex:student>
   </ex:Class>
  </ex:offers>
 </ex:School>
 </ex:contains>
</ex:University>

Second document about the instructor:

<ex:Instructor rdf:about="http://www.milowski.com"
               xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
 <ex:name>Alex Milowski</ex:name>
 <ex:teaches rdf:resource="http://www.sims.berkeley.edu/academics/courses/is290-8/s04/"/>
</ex:Instructor>