Computer games are no longer just for entertainment; they have also become a useful instructional strategy for acquiring knowledge. When games are used for purposes other than strict entertainment they become serious games. The goal of serious games is to enable the player to learn a task, master a strategy or develop a skill. Serious games can be used for education and training in any organization, including military, K-20 education, business and industry. The application of serious games in a wide arena requires an ontology for designing high-quality materials.