Abstract
Ontology can make modeling diagrams more efficient, adaptive, and smarter by explicitly specifying their concepts. This paper is an effort to extract concepts for modeling diagrams and condense them into small numbers. This paper claims that many modeling diagrams (56 diagrams) shared a small number of concepts. An experiment has been conducted to extract concepts for 56 diagrams. The result shows that a small number of concepts are frequently used to describe these diagrams. Condensing the semantic of these diagrams into those concepts and standardizing their definitions will achieve a common understanding for any modeling diagrams.