This study, through the ontological engineering approach, aims at building a conceptual basis that encourages instructional designers in better understanding of learning/instructional theories, which mean that instructional designers can select and integrate appropriate strategies from theories within an instructional context. This paper proposes a methodology of structuring the theories in terms of strategies included in them, in which strategies can be structured independent of paradigms and theories. Keywords. Ontology, instructional design, and learning and instructional theories