What is Ontology?

Ontology is, in simplest form, the science of representing knowledge.

Many years ago, when computer is gaining broader use, Ontology was discussed in terms of Knowledge Representation. That is how knowledge is stored in machines (i.e. computers).

I am googling by entering "ontology" as keywords, and from what Google gave, I picked at least three results I planned to explore further.

1. OWL Web Ontology Language Overview

2. Ontology. Based on well-known John F. Sowa's book.

3. Ontology (computer science) - Wikipedia, the free encyclopedia

4. What is an Ontology? by Tom Gruber of Stanford University's Knowledge Systems Lab.

5. Ontology. A resource guide for philosophers

In recent years, where XML is gathering more attention, Ontology and Semantic Web is chained together. My research interest is in some sense related to Semantic Web research.