This paper describes the achievements of an innovative eight-year research program first introduced in Mizoguchi and Bourdeau (2000), which was aimed at building a theory-aware authoring system by using ontological engineering. To date, we have proposed OMNIBUS, an ontology that comprehensively covers different learning/instructional theories and paradigms, and SMARTIES, a theory-aware and standards-compliant authoring system to create learning/instructional scenarios based on OMNIBUS. This approach was intended to bridge the gap between theory and practice in scientific and technological development, including learning/instruction support. The goals of this study included the following: that computers would (a) understand a variety of learning/instructional theories based on their organization, (b) utilize such understanding to help authors build learning/instructional scenarios, and (c) make such theoretically sound scenarios interoperable within the framework of technology standards. This paper suggests an ontological engineering solution to achieve these three goals and describes the implementation and feasibility demonstrations of the basic functions of SMARTIES, a solution that supports the design of learning/instructional scenarios based on multiple theories. Although the evaluation is far from complete in terms of practical use, we believe that the results of this study speak to high-level technical challenges of ITS authoring systems and the other areas of AIED, and therefore constitute a substantial contribution.