1
|
|
2
|
- OWL
- What can be said in OWL-S
- OWL vs XML
- RDF/RDFS/OWL
- OWL language
- Description Logic
- What do they are good for
- What inference do they support
|
3
|
- Classes: ComputerManifacturer
- Subclasses:
- ComputerManifacturer < Manifacturer
- Instances: IBM
- Properties: products
- Restriction on properties:
- all products are computers
- Cardinality restrictions:
- At lest two production facilities
- Set Theoretic statements:
- At lest two production facilities
|
4
|
- From RDF/RDFS
- XML Syntax
- Concepts of rdfs:subclassOf, rdfs:Property etc…
- From Description Logics
- Axiomatic description
- Proof theory: inference mechanism
- Constraints on the language to maintain inference computable
|
5
|
|
6
|
|
7
|
|
8
|
|
9
|
|
10
|
- Provide basic syntax for OWL
- Use of URI for unique identification of concepts, instances and
relations
- Expression of relations between objects and concepts
|
11
|
- Add basic structure to RDF
- Class/Subclass declaration
- Instances
- Properties (relations)
- Multiple inheritance
- OWL greatly expands the vocabulary of possible constructs
|
12
|
- Subset of First Order Logics used to describe objects in a domain
- Allows three types of objects
- Concepts: describe general concepts of things in the domain
- They are usually represented as sets
- Ex: Bird: the generic description of bird (or whatever is common to
all the things that are birds)
- Individuals: an object in the domain
- Properties: relations between concepts
- One special relation is ISA (or subclassOf)
- Ex: Bird isa Animal or Bird has Wing
- Superficially OO looking
|
13
|
- OWL relies on Description Logics
- Logics provide automatic
- Check of consistency of concept definitions
- Completion of concept definitions
- Classification of new instances and concepts
- Extraction of implicit knowledge in the documents
- None of this is available in XML
- XML Schema provides some of those properties to some extent
|
14
|
- Different types of properties
- Transitivity, Symmetry, Function, Inverse etc…
- Transitivity:
- Joe siblingOf Sally and Sally siblingOf Bob then Joe siblingOf Bob
- Inverse: Joe siblingOf Sally then Sally siblingOf Joe
- Cardinality restrictions
- Specify how many elements are in relation with each other
- at-most, at-least, exactly, optionality (0 or more)
- Bird has (exactly) 2 Wing
- Type restrictions
- Identifies subclasses that have some restriction on a property P
- Bottle madeOf Material
- Glass subclassOf Material
- GlassBottle subclassOf Bottle madeOf Glass
|
15
|
- Equivalence of concepts
- Allows concepts that have been defined in different ontologies to be
equated
- Ont1:LiquidContainer equvalentClass ont2:Bottle
- As a consequence any instance of LiquidContainer iis also an instance
of Bottle and any instance of Bottle is also an instance of LiquidContainer
- Equivalence of individuals
- Allows instances defined in different ontologies to describe the same
objects
- EveningStar sameAs MorningStar
- Difference of individuals
- Assert values that are mutually distinct.
|
16
|
- Complex types to support set theory
- union, intersection and complement
- Human= unionOf Woman and Man
- Enumerated Classes
- means to specify a class via a direct enumeration of its members, this is done through the oneOf
construct
- Gender oneOf male or female
- Disjoint Classes
- It guarantees that an individual that is a member of one class cannot
simultaneously be an instance of a specified other class.
|
17
|
- Inheritance (Subsumption)
- The properties of the super class are inherited to the subclass and
eventually to the instances
- Automatic classification
- You can define a new object of type Thing (the top level node) and
depending on its property that object is automatically classified (and
completed)
- Bird subclassOf Animal with exactly 2 Wing
- Tweedy is an instance of Thing
- Tweedy has wing LeftWing
- Tweedy has wing RightWing
- Tweedy has not more wings
- Tweedy is automatically classified as Bird
|
18
|
- Description Logics provides a snapshot of the World
- Describe objects in a given time frame
- They are intrinsically very static
- Difficult to represent processes (sequences of situations)
- There is no explicit notion of variables and rules
- It is impossible to say that
- X father Y and Y fatherZ Ž X grandfather Z
|
19
|
- Description Logics provides a careful balance between expressivity and
computational complexity
- OWL provides sublanguages with reduced expressivity and computational
complexity
|
20
|
|
21
|
- Full:
- The advantage of the Full version of OWL is that you get the full power
of the OWL language.
- The disadvantage of the Full version of OWL is that it is difficult to
build a Full tool. Also, the
user of a Full-compliant tool may not get a quick and complete answer.
- DL/Lite:
- The advantage of the DL or Lite version of OWL is that tools can be
built more quickly and easily, and users can expect responses from such
tools to come quicker and be more complete.
- The disadvantage of the DL or Lite version of OWL is that you don't
have access to the full power of the language.
|
22
|
- OWL specifications
- W3C page on OWL
- http://www.w3c.org/2001/sw/WebOnt/
- OWL Guide and language reference
- http://www.w3.org/TR/owl-guide/
- http://www.w3.org/TR/owl-ref/
- Tutorials
- Costello and Jacobs’ OWL tutorial: http://www.xfront.com/owl/
|
23
|
|