Cartic Ramakrishnan
LSDIS lab
University of Georgia taken from Schulze-Kremer Steffen

• The study of being qua being : the study of possible
• The study of the nature of possible: ontology as the theory of distinctions among possibilia
• The study of the most general characteristics that anything must have in order to count as a (certain kind of) being or entity .
taken from Schulze-Kremer Steffen

• Ontology (capital “o”):
– a philosophical discipline .
• An ontology (lowercase “o”):
– specific artifact designed with the purpose of expressing the intended meaning of a vocabulary taken from Schulze-Kremer Steffen

• A shared vocabulary
• Plus … A specification (actually, a
characterization) of the intended meaning of that vocabulary
...i.e., an ontology accounts for the commitment of a language to a certain conceptualization
“An ontology is a specification of a

taken from Schulze-Kremer Steffen

• First order logic is ontologically neutral
• Logical KBs often rely on natural language to convey intended meaning
Red(x) this apple is red
"purple" is a red
John i s a red
Apple(x) this is an apple this is apple taken from Schulze-Kremer Steffen

An ontology consisting of just a vocabulary is of little use -
Unintended interpretations need to be excluded
Models M(L)
Intended models I
K
(L) taken from Schulze-Kremer Steffen

a b c d e
Scene 1: blocks on a table
Conceptualization of scene 1:
<{a, b, c, d, e }, {on, above, clear, table }> taken from Schulze-Kremer Steffen

c a b d e
Scene 2: a different arrangement of blocks
The same conceptualization?
taken from Schulze-Kremer Steffen

•
Conceptualization: the formal structure of reality as perceived and organized by an agent, independently of:
– the vocabulary used (i.e., the language used)
– the actual occurence of a specific situation
• Different situations involving the same objects, described by different vocabularies, may share the same conceptualization.
L
E
L
I apple same conceptualization mela taken from Schulze-Kremer Steffen

Intended models I
K
(L)
Conceptualization C
Commitment K=<C,
I
>
Language L
Models M(L)
Ontology taken from Schulze-Kremer Steffen

(SSK would disagree)
• Lexicon
– Vocabulary with NL definitions
• Simple Taxonomy
• Thesaurus
– Taxonomy plus related-terms
• Relational Model (
NOT DB)
– Unconstrained use of arbitrary relations
• Fully Axiomatized Theory taken from Schulze-Kremer Steffen

• Ontology
– study of being as a branch of philosophy
• Ontologies
– result of the analysis of a particular domain of interest (possibly as broad as the universe)
– instantiation of a concrete ontological model of that domain taken from Schulze-Kremer Steffen

• Ontologies are to a large extent in principle language independent
• Varying scope and content of domain ontologies
– upper-level ontologies (Cyc)
– application ontologies (??)
– task ontologies (??) taken from Schulze-Kremer Steffen

• Here are three definitions of domain ontologies
– (i) "System of categories accounting for a particular vision of the world." [ Guarino ]
– (ii) "Specification of a conceptualization."
[ Gruber ]
– (iii) "Concise and unambiguous description of principle relevant entities with their potential, valid relations to each other." [ guess who?
] taken from Schulze-Kremer Steffen

• not a collection of facts arising from a specific situation
• not a model of an application domain
• not a database schema
• not a knowledge base
• not a taxonomy
• not a vocabulary or dictionary
• not a semantic net taken from Schulze-Kremer Steffen

• Data integration
– Semantic integration of n databases
• without the great “o” would require n*n integration attempts
• with the great “o” would require n attempts
• Data annotation
– full-fledged ontology not required
• since main purpose is fixed unique reference point in the for of controlled vocabulary taken from Schulze-Kremer Steffen

• Not ontology but vocabulary
– ISA vs. instance-of
– PART-OF vs “made of”, “belongsto”
– 80% concepts lack explicit defn.
– 700 concepts are orphans
– no clear design principle
– no IC for consistency
– where do new concepts go?
– No grammar rules for to combine concept

• Guarino, N. (1998). Some Ontological Principles for Designing Upper Level
Lexical Resources. In: Proceedings of First International Conference on
Language Resources and Evaluation. Granada, Spain.
• Gruber, T. R. (1993). Knowledge Acquisition 5, 199-220.
•
Schulze-Kremer, S. (1998) Ontologies for molecular biology taken from Schulze-Kremer Steffen