1. Semantic Web - Ontologies
Sameer Totey
9/18/2018
CSCI Web Infrastructure, Services, and Applications

2. CSCI 7818 - Web Infrastructure, Services, and Applications
What is Ontology
Branch of Philosophy that studies nature of existence
Specification of a conceptualization
Document or file that formally defines relations among terms
Shared understanding of some domain of interest
9/18/2018
CSCI Web Infrastructure, Services, and Applications

3. CSCI 7818 - Web Infrastructure, Services, and Applications
This picture is from Tutorial on “Development and applications of Ontologies” by Alexander Maedche
9/18/2018
CSCI Web Infrastructure, Services, and Applications

4. CSCI 7818 - Web Infrastructure, Services, and Applications
9/18/2018
CSCI Web Infrastructure, Services, and Applications

5. What is Ontology for Web ?
A Taxonomy which defines classes of objects and relations among them
A set of inference rules
(Classes subclasses and relations among entities)
9/18/2018
CSCI Web Infrastructure, Services, and Applications

6. CSCI 7818 - Web Infrastructure, Services, and Applications
Why Ontologies?
Lack of a shared understanding leads to poor communication
Disparate modeling paradigms, languages and software tools limit
Interoperability
Knowledge Sharing and reuse
9/18/2018
CSCI Web Infrastructure, Services, and Applications

7. CSCI 7818 - Web Infrastructure, Services, and Applications
Theory
Usually Ontology structure is represented as a 5 Tuple O = (C,R, H, rel, A)
Disjoint Sets C and R are concept identifiers and relation identifiers respectively
H is the concept hierarchy. Also called Taxonomy. H(C1,C2) means C1 is subconcept of C2. H is a directed transitive relation.
Rel is a function that relates concept non-taxonomically, rel : R  C X C
A is a set of ontology Axioms, expressed in an logical language like first order logic.
9/18/2018
CSCI Web Infrastructure, Services, and Applications

8. CSCI 7818 - Web Infrastructure, Services, and Applications
Ontology Engineering
The task of developing an ontology is a typical knowledge acquisition task involving
Kickoff
Refinement
Evaluation
Maintenance
9/18/2018
CSCI Web Infrastructure, Services, and Applications

9. CSCI 7818 - Web Infrastructure, Services, and Applications
Languages
There are several representation languages in the AI (machine learning, natural language processing, knowledge representation etc) community based on FOL like
Frame Logic
Loom
Ontololingua etc.
Web needs XML based language : defining a language on top of XML syntax
SHOE (SHOE is an HTML-based knowledge representation language) Simple HTML Ontology Extention.
XOL (Ontology Exchange Language)
OML (Ontology markup language)
RDFS (Resourse description framework scheme language)
OIL (Ontology Interchange Language)
DAML (DARPA Agent markup language)
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CSCI Web Infrastructure, Services, and Applications

10. CSCI 7818 - Web Infrastructure, Services, and Applications
Editors
Tools that help create ontologies and metadata that can be used by multiple agents:
Protégé
WebOnto
OilEd
ONTOEdit
9/18/2018
CSCI Web Infrastructure, Services, and Applications

11. CSCI 7818 - Web Infrastructure, Services, and Applications
Related issues:
Higher order logic based inference engines – Needed but not feasible
First order logic based inference engines – feasible but limited expressive power, FOL is semi-decidable some inferences are computationally intractable
Interoperability
Bremer Semantic Translation project
SKC (Stanford Scalable Knowledge Composition) project
9/18/2018
CSCI Web Infrastructure, Services, and Applications

12. CSCI 7818 - Web Infrastructure, Services, and Applications
References
[Development and applications of Ontologies] tutorial
9/18/2018
CSCI Web Infrastructure, Services, and Applications

13. CSCI 7818 - Web Infrastructure, Services, and Applications
9/18/2018
CSCI Web Infrastructure, Services, and Applications