Web Ontology Language OWL

1
Web Ontology Language OWL

• Boanerges Aleman-Meza
• CSCI 8350 Enterprise Integration
• Semantic Web Course
• Large Scale Distributed Information Systems
  (LSDIS) Lab

2
Previously

• RDF / RDFS
• Subject, Predicate, Object
• DAML (USA)
• OIL (Europe)
• DAMLOIL (W3C Note) daml
• OWL

3
RDF1

• Athens located_In Georgia
• may not say what Athens, Georgia are
• located_In may imply what Athens is by its
  domain
• located_In may imply what Georgia is by its
  range
• located_In range City, State may be
  very incorrect
• Unless New York located_In New York, or not?

4
RDF2

• Athens located_In Georgia
• located_In range Place
• Does not imply Georgia is a state, but gives
  some meaning to it
• Be careful when using other peoples ontologies
  in RDFS / OWL

5
RDF3

• RDF / RDF Schema has its issues
• Treatment of classes as individuals
• DL not compatible with RDF Schema model theory
• Solid building block for the Semantic Web?
• Do it again, and name it OWL
• More people involved
• More insight about the area

6
OWL, W3C definition

• language for defining structured, Web-based
  ontology
• which enable richer integration
• and interoperability of data
• across
• application bundaries

7
OWL Use Cases

• Web portals
• Multimedia Collections
• Corporate web site management
• Design documentation
• Agents and services
• Ubiquitous computing

8
OWL Design Goals

• Shared ontologies
• Ontology evolution
• Ontology interoperability
• Inconsistency detection
• Expressivity vs. scalability
• Ease of use
• Compatibility with other standards
• Internationalization

9
Whats in OWL, but not in RDF

• Ability to be distributed across many systems
• Scalable to Web needs
• Compatible with Web standards for
• accessibility, and
• Internationalization
• Open and extensible

10
OWL explained

• OWL Overview 12
• OWL Guide 39
• OWL Reference 48
• OWL Semantics and Abstract Syntax 43
• (RDF has a RDF Semantics)
• OWL Test Cases 21
• OWL Use cases and requirements 17
• (tools)

11
OWL distributed

• Someones ontology
• Warning Classes, Properties
• DC domain ? property ? range
• imports
• imports
• imports
• dctitle example

12
OWL open and extensible

• RDF Schema (meta-modeling facilities, i.e.
  classes of classes)
• OWL Full

• OWL DL (Description Logics)

• OWL Lite
• targeting tool builders

13
OWL extensible

• Ontology headers
• prior version
• version info
• backward compatible with
• incompatible with
• deprecated class, deprecated property
• label, comment, see also, is defined by
  (rdfs)

14
owlClass

• Sub class of Class in RDF
• Better to forget about classes of classes
• Top-most class owlThing

15
OWL Properties

• Object
• Properties
• Ana ? owns ? Cuba
• Is range a
• literal / typed value ?
• then ERROR

• Data type
• Properties
• Ana ? age ? 25
• XML Schema data types supported
• DB people happy

16
Transitivity of properties

• X ? p1 ? Y
• Y ? p1 ? Z
• implies X ? p1 ? Z
• Transitivity existed already in RDF
• subClassOf, and ???
• located_in example
• part_of example

17
Symmetric properties

• X ? p1 ? Y
• implies X ? p1 ?Y
• example, p1

18
OWL web needs

• No Unique Names Assumption
• http//www.a.edu/Ana_Zhang_8776
• http//www.b.edu/Ana_Zhang_8776
• http//lsdis.cs.uga.edu/Ana
• http//lsdis.cs.uga.edu/T442
• Same individual?
• Different?
• All different?

19
Functional Properties

• X ? p1 ? Y
• X ? p1 ? Z
• imply Z is the same as Y
• (they describe the same)
• example, p1
• What if Y, Z
• where explicitly defined as different ?

20
Inverse Functional Properties

• Y ? p1 ? A
• Z ? p1 ? A
• imply Z is the same as Y
• (they describe the same)
• example, p1
• What if Y, Z
• where explicitly defined as different ?

21
All values from

• How is different to range
• example
• Also some Values From
• example
• Consistency checking

22
OWL distributed

• equivalent class
• equivalent Property

Guitar
Guitarra
Internationalization standards ?
23
Complex Classes
Female
Student
Professor
Human
Married

• Male
• Students
• Married Female Professors

• Married Female Students
• Divorced

• Minority Students example

24
Disjoint Classes

• Married disjoint with
• Divorced
• Widowed
• Single
• Are Divorced and Single disjoint ?

Married
Widowed
Single
Divorced
25
OWL Cardinality

• min Cardinality
• max Cardinality
• Cardinality
• When min max
• has Value
• belongs to the class if it has the value

26
OWL Tools

• Pellet (umd.edu)
• DLbased reasoner implemented in Java
• Euler
• an inference engine supporting logic based
  proofs. Finds out whether a given set of facts
  support a given conclusion
• FaCT (Ian Horrocks)
• DL classifier that can also be used for modal
  logic satisfiability testing

27
OWL Tools2

• Hoolet
• DL Reasoner that uses a First Order Prover to
  reason about ontologies
• Jena2 (hp)
• sound (but not complete) instance reasoning for
  OWL Lite
• Surnia (MIT/LCS)
• OWL Full reasoner
• Online

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Final Thoughts

• Easy ? unambiguous
• Complex ? harder (usage / build)
• Who cares about errors in HTML ?
• Who cares about XML syntax for OWL ?
• Large Scale test to DL systems
• Is OWL a better base for other languages?
• Whats next?

29
References

• OWL Overview
• OWL Guide
• OWL Reference
• OWL Use cases and requirements