1. 74.419 Artificial Intelligence 2004 Ontology
Ontology Languages
Semantic Web
"Real" Ontologies

2. Ontology Languages and Ontologies
Semantic Web – Ontology languages for Internet organization and search (DAML, OIL, OWL)
Wordnet – based on linguistic descriptions
Cyc – Knowledge Base organization system
Ontolingua – KB development tool (with predefined Ontology), Stanford U.
Microcosmos – Ontology developed for Computational Linguistics, CRL

3. Semantic Web - Ontology
General Ontology Languages (similar to LOOM, based on DL) for the WWW

4. Semantic Web
Definition: The Semantic Web is the representation of data on the World Wide Web. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF), which integrates a variety of applications using XML for syntax and URIs for naming.
"The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation." -- Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001

5. OWL, OIL, and DAML DAML - Agent Markup Language
OIL - Ontology Inference Engine
DAML+OIL - "semantic markup language for Web resources"
integrate Ontology Language with the Resource Description Framework (RDF)
OWL - Web Ontology Language (follower of DAML and OIL; based on DL)
Developed by the WWW Consortium: W3C.

6. DAML+OIL
DAML+OIL is a semantic markup language for Web resources. It builds on earlier W3C standards such as RDF and RDF Schema, and extends these languages with richer modelling primitives. DAML+OIL provides modelling primitives commonly found in frame-based languages. DAML+OIL (March 2001) extends DAML+OIL (December 2000) with values from XML Schema datatypes. [...]
The language has a clean and well defined semantics.

7. DAML+OIL - Example Concept Definition (multiple superclasses):
a Man is a Male Person
<daml:Class rdf:ID="Man"> <rdfs:subClassOf rdf:resource="#Person"/> <rdfs:subClassOf rdf:resource="#Male"/> </daml:Class>

8. hasParent is a relation between animals
DAML+OIL - Example
Relation Definition
hasParent is a relation between animals
<daml:ObjectProperty rdf:ID="hasParent">
<rdfs:domain rdf:resource="#Animal"/>
<rdfs:range rdf:resource="#Animal"/>
</daml:ObjectProperty>

9. OWL - Main Language Constructs
RDF Schema Features:
Class
rdf:Property
rdfs:subClassOf
rdfs:subPropertyOf
rdfs:domain
rdfs:range
Individual

10. OWL - Equality Expressions
(In)Equality:
equivalentClass
equivalentProperty
sameAs (for Individuals)
differentFrom (for Individuals)
allDifferent (for several Individuals)

11. OWL - Combine Class Expressions
Boolean Combinations of Class Expressions:
unionOf
intersectionOf
complementOf

12. OWL - Class Axioms Class Axioms: oneOf (describe enumerated classes)
disjointWith
equivalentClass (for class expressions)
rdfs:subClassOf (for class expressions)

13. OWL- Properties Property Characteristics: InverseOf TransitiveProperty
SymmetricProperty
FunctionalProperty
InverseFunctionalProperty

14. OWL- Properties Property Type Restrictions: allValuesFrom
someValuesFrom
Filler Information:
hasValue
Arbitrary Cardinality:
minCardinality
maxCardinality
cardinality

15. Reasoning with Ontologies
Classifier
Consistency Check
Check for Implied Relatonships
Compare and Combine Different Ontologies

16. How to fill this framework given by general Ontology Languages?
Ontology - Contents
How to fill this framework given by general Ontology Languages?

17. What is Ontology?
The analysis and description of how the world is structured. (my definition)
"That department of the science of metaphysics which investigates and explains the nature and essential properties and relations of all beings, as such, or the principles and causes of being." (Webster's)
"the metaphysical study of the nature of being and existence" (WordNet)
"<philosophy> A systematic account of Existence." (Free On-line Dictionary of Computing)

18. What is Ontology?
"<artificial intelligence> (From philosophy) An explicit formal specification of how to represent the objects, concepts and other entities that are assumed to exist in some area of interest and the relationships that hold among them." (Free On-line Dictionary of Computing)

19. "Real" Ontology Ontology
looks for semantic and ontological primitives and concepts to describe aspects or parts of “the world”
aim of research is to develop KBs which can be shared and commonly used in various contexts, i.e. for different applications and different fields (e.g. for NLP, reasoning, planning etc.)
relates to psychology and philosophy, as well as data bases and object-oriented programming systems

20. Ontologies – Background
Ontology – Conceptual Hierarchy
Wittgenstein (philosophy and language) – “Family Resemblances” instead of exact concept definitions
Eleanor Rosch (cognitive psychology) – Prototype Theory; natural concepts

21. Constructing Ontologies
Basic elements of ontology languages
Concepts & IS-A Hierarchy
Roles, Relations w. specification
Features, Attributes, Slots w. specification
Instances (concrete objects)
Assertions (facts about objects in the world)
Axioms (define the world; describe general rules of the world)

22. Basic Concepts in Ontologies
Physical Objects
Stuff and Things; Composite Objects
Fluids
Substances
Actions and Events
happen in time; agent or natural cause or no cause
modeling dynamic aspects problematic
Abstract Objects
abstract concepts (ideas) like 'freedom'
difficult to define and describe

23. Basic Concepts in Ontologies
Physical structures
Time
Space
Mathematical structures
Sets, Groups, ...

24. Web References Description Logics Page www.dl.kr.org LOOM
Ontology Page
Ontolingua Home Page
Open Cyc