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Untitled Prezi

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wala abdulaziz

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In computer science and information science, an ontology formally represents knowledge as a set of concepts within a domain, and the relationships between pairs of concepts. It can be used to model a domain and support reasoning about entities. What is ontology? Why we need ontology? To share common understanding of the structure of information among people or applications.

To enable reuse of domain knowledge: when we have ontology on a domain, we can reuse the same ontology on different applications, so we don't have to re-inventing the wheel.

To make domain assumptions explicit

To separate domain knowledge from the operational knowledge

To analyze domain knowledge: By using appropriate relation between concepts Importance of the ontology OWL and Protege A shared ontology of
Pizaa Ontology Engineering Process Determine scope of the domain.
Enumerate Terms that we will used in the domain.
Define classes that represent concepts of the domain.
Define properties for our classes to link it together.
Define constraints which restrict classes and properties.
Create instances from classes. Web Ontology Language (OWL) Language for defining the Web ontologies.

An OWL ontology may include descriptions of classes, properties and their instances. Given such an ontology, the OWL formal semantics specifies how to derive its logical consequences What is the Protégé? Protege is a graphical ontology-development tool supports a rich knowledge model.

It is open-source and freely available. Components of OWL Ontologies 1- Individuals Individuals represent objects in the domain in which we are interested.

Individuals are also known as instances.

Individuals can be referred to as being `instances of classes'. Components of OWL Ontologies 2- Properties Properties are binary relations on individuals. On other word, properties link two individuals together. Components of OWL Ontologies 3- Classes OWL classes are interpreted as sets that contain individuals.
They are described using formal descriptions that state precisely the requirements for membership of the class.
Classes may be organized into a superclass-subclass hierarchy. Pizza Example Active ontology Classes Classes OWL Properties The pizza ontology have many classes. Subclasses : in OWL means implication. Disjoint classes: Separate a group of classes (If A is disjoint from B, then an individual of
class A cannot also be an individual of class B.) We make these classes disjoint:
IceCream
Pizaa
PizzaBase
PizzaTopping
Object properties are relationships between two individuals. It links an individual to an individual.


Relationships between an individual and data values


Annotation properties using to add information (metadata or data about data) to classes, individuals and object / data type properties. Object properties: Datatype properties: Annotation properties: Object properties Object properties hasCountryOfOrigin
hasIngredient:
haseBase
hasTopping
hasSpiciness
isIngerdientOf:
isBaseOf
isToppingOf Property Domains and Ranges Properties link individuals from the domain to individuals from the range. hasBase property Reasoner is one of the important function in Protégé. We use the reasoner to determine class inconsistencies and discovering implicit information using necessary and sufficient conditions. Reasoner Reasoner Consistency checking: Test whether a class could have instances. Classification: A classifier takes a class hierarchy and places a class in the class hierarchy. Reasoner The classes appear in red mean it is inconsistent. Inconsistent on ontology means the impossibility for any class to have any instance. CheeseyVegetableTopping is Inconsistent because we have given it 2 disjoint parents CheeseTopping and VegetableTopping. Reasoner Note: If we make CheeseTopping and a VegetableTopping not disjoint from each other, then invoke resoner again the CheeseyVegetableTopping class will not be an inconsistent. OWLViz view and navigate our classes .
check the consistency and show the logical meaning as a tree.
Helpful in huge ontologies which have classes with many super classes.
asserted classes hierarchy
inferred classes hierarchy OWLViz provide: Inferred classes hierarchy Inconsistent classes The inconsistent classes are highlighted in red. Adding some classes to Pizza example
(Drinks Classes) Live Demo
Asserted classes hierarchy Questions? References 1- Ontology (information science): http://en.wikipedia.org/wiki/Ontology_(information_science)
2- Natalya F. Noy, Deborah L. McGuinness, Ontology Development 101: A Guide to Creating Your First Ontology, Stanford, Available from:
http://www.ksl.stanford.edu/people/dlm/papers/ontology-tutorial-noy-mcguinness.pdf
3- What is protégé?: http://protege.stanford.edu/overview/index.html
4- W3C,(2004)OWL Web Ontology Language Guide: http://www.w3.org/TR/owl-guide/
5- Protégé Glossary:
http://protegewiki.stanford.edu/wiki/Pr4_UG_mi_Glossary#FaCT.2B.2B
6- Matthew Horridge, (2011) A Practical Guide To Building OWL Ontologies
Using Protege 4 and CO-ODE Tools [online] Manchester, Available from:
http://owl.cs.manchester.ac.uk/tutorials/protegeowltutorial/resources/ProtegeOWLTutorialP4_v1_1.pdf 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 20 21 22 23 24 25 26 27 28 Object properties Functional Properties: If a property is functional, for a given individual, there can be at most one individual that is related to the individual via the property. Functional properties are also known as single valued properties. Example: hasBase property. Object properties Inverse Functional Properties: If a property is inverse functional then it means that the inverse property is functional. Object properties Transitive Properties: If a property is transitive, and the property relates individual a to individual b, and also individual b to
individual c, then we can infer that individual a is related to individual c via property P. Object properties Symmetric Properties: If a property P is symmetric, and the property relates individual a to individual b then individual b is also related to individual a via property P. Asymmetric properties: If a property P is asymmetric, and the property relates individual a to individual b then individual
b cannot be related to individual a via property P. Example: 1- isIngredientOf
2- hasIngredient Example: 16 17 18 hasIngredient 19 Presented by:
Wala Alnasser 6-5-2013
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