This document provides an overview of an ontology engineering tutorial being conducted as part of the PalGov project. It includes information about the project consortium and funding, a tutorial map outlining the sessions and their learning objectives, and background information about ontologies. Specifically, it defines an ontology as an explicit specification of a conceptualization written in logic as a set of axioms. It distinguishes between ontologies and conceptual data schemas by noting that ontologies provide meaning for concepts and relations in addition to structure.

1. ‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps
Tutorial 4: Ontology Engineering & Lexical Semantics
Session 1.2
What is an Ontology
Dr. Mustafa Jarrar
University of Birzeit
mjarrar@birzeit.edu
www.jarrar.info
PalGov © 2011 1

2. About
This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the
Commission of the European Communities, grant agreement 511159-TEMPUS-1-
2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )
Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium
Palestine Technical University, Palestine
Université de Savoie, France
Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine
Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

3. © Copyright Notes
Everyone is encouraged to use this material, or part of it, but should
properly cite the project (logo and website), and the author of that part.
No part of this tutorial may be reproduced or modified in any form or by
any means, without prior written permission from the project, who have
the full copyrights on the material.
Attribution-NonCommercial-ShareAlike
CC-BY-NC-SA
This license lets others remix, tweak, and build upon your work non-
commercially, as long as they credit you and license their new creations
under the identical terms.
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4. Tutorial Map
Topic Time
Session 1_1: The Need for Sharing Semantics 1.5
Session 1_2: What is an ontology 1.5
Intended Learning Objectives
A: Knowledge and Understanding Session 2: Lab- Build a Population Ontology 3
4a1: Demonstrate knowledge of what is an ontology, Session 3: Lab- Build a BankCustomer Ontology 3
how it is built, and what it is used for. Session 4: Lab- Build a BankCustomer Ontology 3
4a2: Demonstrate knowledge of ontology engineering
and evaluation. Session 5: Lab- Ontology Tools 3
4a3: Describe the difference between an ontology and a Session 6_1: Ontology Engineering Challenges 1.5
schema, and an ontology and a dictionary.
Session 6_2: Ontology Double Articulation 1.5
4a4: Explain the concept of language ontologies, lexical
semantics and multilingualism. Session 7: Lab - Build a Legal-Person Ontology 3
B: Intellectual Skills Session 8_1: Ontology Modeling Challenges 1.5
4b1: Develop quality ontologies. Session 8_2: Stepwise Methodologies 1.5
4b2: Tackle ontology engineering challenges.
4b3: Develop multilingual ontologies. Session 9: Lab - Build a Legal-Person Ontology 3
4b4: Formulate quality glosses. Session 10: Zinnar – The Palestinian eGovernment 3
C: Professional and Practical Skills Interoperability Framework
4c1: Use ontology tools. Session 11: Lab- Using Zinnar in web services 3
4c2: (Re)use existing Language ontologies.
Session 12_1: Lexical Semantics and Multilingually 1.5
D: General and Transferable Skills
d1: Working with team. Session 12_2: WordNets 1.5
d2: Presenting and defending ideas. Session 13: ArabicOntology 3
d3: Use of creativity and innovation in problem solving.
Session 14: Lab-Using Linguistic Ontologies 3
d4: Develop communication skills and logical reasoning
abilities. Session 15: Lab-Using Linguistic Ontologies 3
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5. Session ILOs
This session will help student to:
4a1: Demonstrate knowledge of what is an ontology, how it is
built, and what it is used for.
4a3: Describe the difference between an ontology and a
schema, and an ontology and a dictionary.
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6. Reading Material
0) Everything in these slides
1)Thomas R. Gruber: Toward Principles for the Design of Ontologies Used for
Knowledge Sharing http://tomgruber.org/writing/onto-design.pdf
2) Nicola Guarino: Formal Ontology and Information Systems http://www.loa-
cnr.it/Papers/FOIS98.pdf
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7. What is an Ontology?
In Philosophy
Ontology as such is usually contrasted with Epistemology, which
deals with the nature and sources of our knowledge [a.k.a. Theory of
Knowledge]. Aristotle defined Ontology as the science of being as
such: " unlike the special sciences, each of which investigates a class
of beings and their determinations, Ontology regards all the species of
being qua being (‫ )كينونات‬and the attributes (‫ )صفات‬which belong to it qua
being" (Aristotle, Metaphysics, IV, 1).
• It is the science of what is (in the universe) .
• Ontos (that which exists) + logos (knowledge of)
• Dates back to Artistotle
• Quine, 1969: “To exist is to be the value of a quantified variable”
(‫)األنطولوجيا: علم الوجود بما هو موجود‬
 So, it is a science (branch of philosophy): Analytical Philosophy ‫الفلسفة التحليلية‬
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8. What is an Ontology?
In computer science
– McCarthy (1980) calls “a list of things that exist” an ontology.
– Gruber (1995): “an explicit specification of a conceptualization”.
– Welty (later): “Description of the kinds of entities there are and how
they are related”.
– Some people refer to as a domain model or a conceptual model.
– To simplify it:
Once my grandmother asked me about my research, I said
“ontology”, she said what it this? I said: “it is a dictionary that
computers can understand”. She said, how? I said, the computer
computes the meaning as it is represented in logic.
 Note that “ontology” here is not a new name for an old thing.
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9. What is an Ontology?
• An ontology is ...
– an explicit specification of a conceptualization [Gruber93]
– a shared understanding of some domain of interest [Uschold,Gruninger96]
• Some aspects and parameters:
– a formal specification (reasoning and “execution”)
– ... of a conceptualization of a domain (community)
– ... of some part of world that is of interest (application)
• Provides:
– A common vocabulary of terms
– Some specification of the meaning of the terms (semantics)
– A shared “understanding” for people and machines
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10. What is an Ontology?
In computer science
Gruber (1995): “a explicit specification of a conceptualization”.
Written in logic, as a set the set of objects and relations in a
of axioms i.e. a theory domain. <Objects,Relations,Functions>
Conceptualization
a = <Objects, Relations, Functions>
b d
c e
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11. What is an Ontology?
In computer science
Gruber (1995): “a explicit specification of a conceptualization”.
Written in logic, as a set the set of objects and relations in a
of axioms i.e. a theory domain. <Objects,Relations,Functions>
Conceptualization:
The ontology is a set of axioms used
Block {a, b, c, d, e} to specify this conceptualization:
a
On {<a,b>,<b,c>,<d,e>} x y On(x,y)  Above(x,y)
b d Above {<a,b>,<b,c>,<d,e>} …
Clear {<a>,<d>}
c e
Table {<c>,<e>}
Hat {<b,a>,<c,b>,<e,d>} Sharing these axioms (i.e., ontology)
means sharing the same understanding
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12. What is an Ontology?
In computer science
Gruber (1995): “a explicit specification of a conceptualization”.
Written in logic, as a set the set of objects and relations in a
of axioms i.e. a theory domain. <Objects,Relations,Functions>
Conceptualization:
Guarino’s:
a d
Block {a, b, c, d, e}  This change implies changing
On {<a,b>,<b,c>,<d,e>} the conceptualization.
b Above {<a,b>,<b,c>,<d,e>}  Do we need to change our
Clear {<a>,<d>}
c e conceptualization each time
Table {<c>,<e>}
there is some re-
Hat {<b,a>,<c,b>,<e,d>}
arrangements in the world?!
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13. What is an Ontology?
In computer science
Gruber (1995): “a explicit specification of a conceptualization”.
Written in logic, as a set the set of objects and relations in a
of axioms i.e. a theory domain. <Objects,Relations,Functions>
Conceptualization:
Block {a, b, c, d, e}
Guarino’s:
a d  this conceptualization is a state
On {<a,b>,<b,c>,<d,e>}
b of affairs (= one situation a
Above {<a,b>,<b,c>,<d,e>}
snapshot) of the domain.
Clear {<a>,<d>}
c e
Table {<c>,<e>}
 This definition of
Hat {<b,a>,<c,b>,<e,d>}
conceptualization has a
problem.
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14. Guarino’s definition of a conceptualization
independent of any specific interpretation,
model, or situation,
A conceptualization is an intensional semantic structure,
which encodes the implicit rules constraining the structure of a piece of
reality
 These should not be ordinary
relations, but rather
conceptual relations.
Conceptualization:
a [[Block]]D {a, b, c, d, e}  A relations has a
b d [[On]]D {<a,b>,<b,c>,<d,e>}
model.
[[Above ]]D {<a,b>,<b,c>,<d,e>} (extensional interpretation).
c e [[Clear ]]D {<a>,<d>}
[[Table ]]D {<c>,<e>}  A conceptual relation has
[[Hat ]]D {<b,a>,<c,b>,<e,d>}
intended models.
(Intensional interpretation).
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15. Guarino’s definition of a conceptualization
independent of any specific interpretation,
model, or situation,
A conceptualization is an intensional semantic structure,
which encodes the implicit rules constraining the structure of a piece of
reality
Ordinary relations are defined on a domain D
Conceptual relations are defined on a domain space <D, W>
An Ontology is an artifact designed with the purpose of expressing the
intended meaning of a (shared) vocabulary.
• A shared vocabulary plus a specification (characterization) of its
intended meaning
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16. How can we formally describe the meaning
of a vocabulary?
Given the “Palestinian Government” domain.
How can we formally describe the meaning of the vocabulary (citizen,
company, salary, tax, car, land, etc.) in this domain?
Example: Company = a type of legal person, registered to conduct
business, and recognized by its registration number. There are two types of
companies: Shareholding Company and Partnership Companies.
In logic: LegalPerson
Company ⊑ LegalPerson Conducts
⊓ Conduct.Business Business
⊓ Has.RegestrationNumber Company
Has
ShareholdingCompany ⊑ Company Registration
Number
PartnershipCompany ⊑ Company
Shareholding Partnership
Company Company
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17. How can we formally describe the meaning
of a vocabulary?
 Notice that meaning/semantics of “Company” can
be determined from its position in the diagram,
i.e., it is relations with other concepts, and
constraints.
Example: Company = a type of legal person, registered to conduct
business, and recognized by its registration number. There are two types of
companies: Shareholding Company and Partnership Companies.
In logic: LegalPerson
Company ⊑ LegalPerson Conducts
⊓ Conduct.Business Business
⊓ Has.RegestrationNumber Company
Has
ShareholdingCompany ⊑ Company Registration
Number
PartnershipCompany ⊑ Company
Shareholding Partnership
Company Company
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18. How can we formally describe the meaning
of a vocabulary?
• Ministries need such precision and formal definitions to exchange data
meaningfully.
• We may use ORM/ER/UML as a language to specify the meaning (i.e.,
semantics) of a domain, as a formal notations. OWL is the standard
ontology language.
 Thus, an ontology consists of Concepts, Relations between these
concepts, and some Rules.
 The most important relation is the subtype relation.
In logic: LegalPerson
Company ⊑ LegalPerson Conducts
⊓ Conduct.Business Business
⊓ Has.RegestrationNumber Company
Has
ShareholdingCompany ⊑ Company Registration
Number
PartnershipCompany ⊑ Company
Shareholding Partnership
Company Company
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19. Part of the LegalPerson Ontology, in Palestine
 The meaning of
each of these
concepts can be
determined from its
position
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20. Ontology vs Conceptual data Schema
• But can we say that an ontology is a conceptual schema?
i.e., is it true that the Palestinian government ontology is a conceptual database schema
covering all data elements in all government databases?
The answer is No!
Then what is the difference between an ontology and a schema?
DB schema provides skeleton/structure to the data, not meaning.
Although ontology provides structure to the data, but the meaning is the
most important aspect.
In logic: LegalPerson
Company ⊑ LegalPerson Conducts
⊓ Conduct.Business Business
⊓ Has.RegestrationNumber Company
Has
ShareholdingCompany ⊑ Company Registration
Number
PartnershipCompany ⊑ Company
Shareholding Partnership
Company Company
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21. Is this an Ontology or a Data Schema?
Address
Has
Person ⊑ HasAddress.String
⊓ hasEmail
Person
Has Email
In OWL
<owl:Class rdf:ID=“Person" />
<owl:Class rdf:ID=“Address" />
<owl:Class rdf:ID=“email" />
<owl:DataProperty rdf:ID=“Has-Address">
<rdfs:domain rdf:resource="#Person" />
<rdfs:range rdf:resource="www.w3.org/2001/XMLSchema#string"/>
</owl:ObjectProperty>
<owl:DataProperty rdf:ID=“Has-Email">
<rdfs:domain rdf:resource="#Person" />
<rdfs:range rdf:resource="www.w3.org/2001/XMLSchema#string"/>
</owl:ObjectProperty>
 What makes and ontology an ontology, not a schema?
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22. Where is the meaning (example: What is X?)
Educational Has Email
Institution
Has Address
X
Project
participates-In/
Faculties
Composed-Of /
If you can be sure of what is X from its position, then its characteristics
(i.e., relations with other concepts) are suitable for defining its meaning?
Which of these characteristics are more distinguishing?
(Intrinsic verse extrinsic characteristics)
“An intrinsic property (‫ )الصفة الجوهرية‬is typically something inherent to an individual, not
dependent on other individuals, such as having a heart or having a fingerprint. Extrinsic
properties (‫ )الصفات العرضية‬are not inherent, and they have a relational nature, like “being a
friend of John”. Among these, there are some that are typically assigned by external agents or
agencies, such as having a specific social security number, having a specific customer ID, or
even having a specific name.” [GW00]
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23. Where is the meaning (example: What is X?)
Educational Has Email
Institution
Has Address
X
Project
participates-In/
Faculties
Composed-Of /
• An ontology that doesn’t hold intrinsic properties is not a good ontology, it
becomes a schema, with poor or no meaning.
• Ideally, it should “...catch all and only the intended meaning” [Gangemi 04]
• Notice that having all and only the intrinsic properties is :
(i) very difficult to represent ,e.g. how to represent “person has brain”,
(ii) such properties are not needed in IT applications, so why to have them.
• Thus, it is not necessary that the intrinsic properties be explicitly captured
in the ontology, but these properties must govern the way we think and
build the ontology. PalGov © 2011 23

24. Where is the meaning (example: What is X?)
Educational Has Email
Institution
Has Address
X
Project
participates-In/
Faculties
Composed-Of /
• Hence, you (as a knowledge engineer) should be smart when making
choices, so to achieve a general but applicable ontology, and not to end
with a schema.
• The more a knowledge engineer is aware of ontology modeling
challenges, the better his/her skills will be in building quality ontologies.
There are some methodologies to guide you building quality ontologies)
(Ontology Modeling Challenges and Methodologies will be discussed later)
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25. The Ontological Level
[Guarino]
Level Primitives Interpretation Main feature
Logical Predicates, Arbitrary Formalization
functions
Epistemological Structuring Arbitrary Structure
relations
Ontological Ontological Constrained Meaning
relations
Conceptual Conceptual Subjective Conceptualization
relations
Linguistic Linguistic Subjective Language
terms dependence
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26. References
1)Thomas R. Gruber: Toward Principles for the Design of Ontologies
Used for Knowledge Sharing http://tomgruber.org/writing/onto-design.pdf
2) Nicola Guarino: Formal Ontology and Information Systems
http://www.loa-cnr.it/Papers/FOIS98.pdf
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