Ontology Construction and Evaluation

I am writing on this topic because I am very much interested on it. At fist, we need to clarify some of questions:

1. What is Ontology ?
2. What is Ontology tool?
3. Why we need to Evaluate it?

My point of view , Ontology is conceptual presentation that bears one scenario of a real world.
But famous definition "An explicit specification of a conceptualization".


There are lots of ontology construction tools around the world. The most famous tool is Protege from Standford University.

Ontology construction is very costly and time consuming. For example, If we want to capture all knowledge of one organization, the solution is ontology. Now, we need to check ontology construction tools so that we can design ontology with minimum cost.