1. ece 627 intelligent web: ontology and beyond
lecture 2: ontology - basics

2. ontology
a branch of metaphysics relating to the nature and relations of being a particular theory about the nature of being or the kinds of existence
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3. ontology & history tree of Porphyry
Supreme: SUBSTANCE Differentiae: material immaterial Subordinate: BODY SPIRIT Differentiae: animate inanimate Subordinate: LIVING MINERAL Differentiae: sensitive insensitive Subordinate: ANIMAL PLANT Differentiae: rational irrational Subordinate: HUMAN BEAST Individuals: Socrates Plato Aristotle etc.
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4. ontology generic
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5. ontology domain-based
the subject of ontology is the study of the categories of things that exist or may exist in some domain
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6. ontology domain-based
the product of such a study, called an ontology, is a catalog of the types of things that are assumed to exist in a domain of interest from the perspective of a person who uses a specific language for the purpose of talking about the domain
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7. ontology domain-based – definition 1
a formal, explicit specification of a shared conceptualization
[T.Gruber, 1993]
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8. ontology domain-based
conceptualization refers to an abstract model of phenomena in the world by having identified the relevant concepts of those phenomena explicit means that the type of concepts used, and the constraints on their use are explicitly defined
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9. ontology domain-based
formal refers to the fact that the ontology should be machine readable shared reflects that ontology should capture consensual knowledge accepted by the communities
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10. ontology domain-based – definition 2 (W3C)
ontology is a term borrowed from philosophy that refers to the science of describing the kinds of entities in the world and how they are related
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11. ontology … description of …
classes (“things”) in the various domains of interest
relationships among those “things”
properties (attributes) that “things” should possess
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12. ontology example
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13. ontology example
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14. ontology vs taxonomy
taxonomy the study of the general principles of scientific classification – systematics classification – especially – orderly classification of plans and animals according to their presumed natural relationships
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15. ontology vs taxonomy
taxonomy classifies terms hierarchically, using (generalization, is-a, or type-of) relationship - no other relationships - no attributes/features describing terms
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16. ontology vs taxonomy (example)
- Linnaean living being taxonomy
Kingdom: animalia
Filo: chordata
Subfilo: vertebrata
Class: mamalia
Subclass: theria
Order: primata
Suborder: anthropoidea
Family: hominidae
Genera: homo
Species: sapiens
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17. ontology vs taxonomy (example)
- directory structure in a personal computer
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18. ontology vs thesauri
thesauri contains a set of relationships among concepts, organized in a taxonomic way it is a taxonomy with a set of semantic (binary) relationships, such as, equivalence, inverse, and association
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19. ontology vs thesauri
not sufficient to model other (part-of, member-group, cause-effect, …) aspects of real world the most popular thesaurus - WordNet
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20. ontology vs thesauri - WordNet
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21. ontology vs thesauri - WordNet
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22. ontology vs thesauri - WordNet
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23. ontology ”unique” properties – 1
strict subconcept hierarchy organization of terms must follow the generalization relationship – is-a, type-of relationship
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24. ontology ”unique” properties – 2
ambiguity-free interpretation of meanings and relationships users may define properties (with values restricted to certain domains) and more expressive relationships (part-of, ……………)
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25. ontology ”unique” properties – 3
the use of a controlled, finite, but extensible vocabulary
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26. ontology classification according to semantic spectrum
based on the internal structure and contents of ontolgoies depends on the complexity and sophistication of the elements the spectrum ranges from informal catalogues of terms to sophisticated ontologies
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27. ontology classification according to semantic spectrum
controlled vocabularies (finite lists of terms)
glossaries (lists of terms whose meaning is described in natural language)
Thesauri (lists of terms … and specific relationships between the terms)
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28. ontology classification according to semantic spectrum
informal is-a hierarchies (hierarchies that use generalization relationships in an informal way – not rigorously)
formal is-a hierarchies (hierarchies that fully respect the generalization relationships)
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29. ontology classification according to semantic spectrum
frames (models that include classes and properties; the primitives of the frame model are classes, or frames, that have properties called slots or attributes; slots may contain default values, refer to other frames, or contain different methods)
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30. ontology classification according to semantic spectrum
ontologies that express value restrictions (contain constructs for restricting the values the class properties can assume)
ontologies that express logical restrictions (allow first-order logic restrictions to be expressed)
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31. ontology classification according to ontology generality
upper-level ontologies (describe generic concepts, such as space, time, events …)
domain ontologies (describe vocabulary pertaining to a given domain, by specializing the concepts provided by the upper-level ontology)
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32. ontology classification according to ontology generality
task ontologies (describe vocabulary required to perform generic tasks or activities, by specializing the concepts provided by the upper-level ontology)
applications ontologies (describe vocabulary of a specific application, whose concepts correspond to the roles performed by entities in a given domain while performing some task or activity)
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33. ontology classification according to represented info
based on “orthogonal”, to previous slides, classification
knowledge-representation ontologies (provide primitive modeling elements – classes, subclasses, value, …)
generic and common use ontologies (represent common-sense knowledge that can be used in different domains; vocabulary that relates classes, events, space, causality, and behavior)
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34. ontology classification according to represented info
upper ontologies (describe
general concepts,
for example SUMO)
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35. ontology classification according to represented info
domain ontologies (offer concepts that can be reused in a specific domain – medical, law, …; sth between upper and domain ontologies)
task ontologies (describe vocabulary related to a task or activity)
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36. ontology classification according to represented info
domain-task ontologies (are task ontologies that can be reused in one specific domain)
method ontologies (provide definitions for concepts and relationships relevant to a process)
application ontologies (contain all necessary concepts to model the application in question)
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37. ontology description languages
1967 – markup language (structure of documents with help of tags) SGML – Standard Generalization Markup Language 1989 – HTML (HyperText Markup Language) XML (Extensible Markup Language)
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38. ontology description languages
RDF (Resource Markup Language) – representing information about resources in the web RDF Schema SHOE (Simple HTML Ontology Extension) Oil (Ontology Inference Layer) DAML (DARPA Agent Markup Language)
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39. ontology description languages
2001 – DMAL+Oil Feb 10th, 2004 – OWL (Web Ontology Language)
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