Ontology has been attracting a lot of attention recently. While ontology research begun in the early 90’s in the knowledge base community, the research activity has been accelerated and spread over the web technology community by the semantic web movement in the last few years. Many people talk about ontology nowadays. However, there seems to be some misunderstandings about what ontology is and what ontological engineering is, how it is useful, etc. The purpose of this paper is to clarify issues on ontology and ontological engineering and to describe the author’s personal views on how ontological engineering should contribute to the future knowledge processing.
ONTOLOGY
Overview
Ontology has been attracting a lot of attention recently. While ontology research begun in the early 90’s in the knowledge base community, the research activity has been accelerated and spread over the web technology community by the semantic web movement in the last few years. Many people talk about ontology nowadays. However, there seems to be some misunderstandings about what ontology is and what ontological engineering is, how it is useful, etc. The purpose of this tutorial is to clarify issues on ontology and ontological engineering and to describe the author’s personal views on how ontological engineering should contribute to the future knowledge processing.
What Is Ontology?
In a lay man’s term, ontology is the theory of being as such. It was originally called “first philosophy” by Aristotle. In the 18th century Christian Wolff contrasted ontology, or general metaphysics, with special metaphysical theories of souls, bodies, or God, claiming that ontology could be a deductive discipline revealing the essences of things. This view was later strongly criticized by David Hume and Immanuel Kant. Ontology was revived in the early 20th century by practitioners of phenomenology and existentialism, notably Edmund Husserl and his student Heidegger. The American heritage dictionary defines Ontology as a philosophical inquiry into the nature of being itself, a branch of metaphysics. While Aristotle defined ontology as the science of being as such. The science of being is used in many different senses. It is sometimes considered to be identical to metaphysics, but preferably used in a more specific sense, as that part of metaphysics that specifies the most fundamental categories of existence and elementary substances or structures out of which the world is made.
Of late, the field of ontology has become a popular technique in Artificial Intelligence. It is used to define the building blocks out of which models of the world are made. Hence it is referred to as the basic level of a knowledge representation.
Ontology deals with the nature and the organization of reality and it tries to answer questions like "what is existence?", "what properties can explain existence?”, among others. Unlike the special sciences, each of which investigates a class of beings and their determinations, ontology regards all the species as qua being and the attributes that belong to it qua being.
Ontology is a formal, explicit specification of a shared conceptualization. Whereby a “conceptualization" is an abstract model of a phenomenon, created by identification of the relevant concepts of the phenomenon. The concepts, the relations between them and the constraints on their use are explicitly defined. "Formal" means that Ontology is machine-readable and excludes the use of natural languages. For example, in medical domains, the concepts are diseases and symptoms, the relations between them are causal and a constraint is that a disease cannot cause itself. Ontology is a "shared conceptualization" states that Ontologies aim to represent consensual knowledge intended for the use of a group. Ideally the Ontology captures knowledge independently of its use and in a way that can be shared universally, but practically different tasks and uses call for different representations of the knowledge in Ontology
Definitions
There are many interpretations about what ontology is. In fact, hot discussions are often done in many meetings on ontology.
1) In philosophy, it means theory of existence. It tries to explain what is being and how the world is configured by introducing a system of critical categories to account things and their intrinsic relations.
2) From AI point of view, ontology is defined as “explicit specification of conceptualization”.
3) From a knowledge-based systems point of view, it is defined as “a theory (system) of concepts/ vocabulary used as building blocks of an information processing system” (Mizoguchi, 1995). In a context of problem solving, ontologies are divided into two types: Task ontology for problem solving process and domain ontology for the domain where the task is performed.
4) Gruber] defines ontology as an agreement about shared conceptualizations where shared conceptualizations include conceptual frameworks for modeling domain knowledge; content-specific protocols for communication among inter-operating agents; and agreements about the representation of particular domain theories.
In the knowledge sharing context, ontologies are specified in the form of definitions of representational vocabulary. A very simple case would be a type hierarchy, specifying classes and their sub-assumption relationships. Relational database schemas also serve as ontologies by specifying the relations that can exist in some shared database and the integrity constraints that must hold for them.
Thus an ontology consists of concepts, hierarchical (is-a) organization of them, relations among them (in addition to is-a and part-of), axioms to formalize the definitions and relations.
Why Study Ontology?
Frequently Asked Questions about Ontology
What is Ontology?
Ontology, in a general sense, is the theory of being. It explores the nature of existence and the fundamental categories of things that exist. In Artificial Intelligence, it's used to define the building blocks of models of the world, acting as a basic level of knowledge representation. It's a formal, explicit specification of a shared conceptualization.
How is Ontology defined in different fields?
The definition of ontology varies depending on the field:
- Philosophy: The theory of existence, explaining being and the world through critical categories and intrinsic relations.
- Artificial Intelligence: Explicit specification of conceptualization.
- Knowledge-Based Systems: A theory (system) of concepts/vocabulary used as building blocks of an information processing system. This can be further divided into task ontology (for problem-solving processes) and domain ontology (for the domain where the task is performed).
- Knowledge Sharing: Agreement about shared conceptualizations, including conceptual frameworks for modeling domain knowledge, communication protocols, and agreements about domain theory representation.
What does an Ontology consist of?
An ontology typically consists of:
- Concepts
- A hierarchical (is-a) organization of these concepts
- Relations among the concepts (is-a and part-of relationships)
- Axioms to formalize the definitions and relationships
Why is Ontology studied?
Ontology has gained prominence, moving from AI labs to domain experts' desktops and the World Wide Web. This is due to its explicit formal specification of terms within a domain and the relationships between them.
What is meant by "shared conceptualization" in the definition of Ontology?
"Shared conceptualization" indicates that ontologies aim to represent consensual knowledge intended for use by a group. Ideally, an ontology captures knowledge independently of its use and in a way that can be shared universally, but practically, different tasks and uses call for different representations of the knowledge in Ontology
- Arbeit zitieren
- Alikira Richard (Autor:in), 2012, Ontology the novice perspective, München, GRIN Verlag, https://www.hausarbeiten.de/document/206341
