Authoring ITS domain models is a difficult task requiring many skills. We explored whether modeling ontology reduces the problem by giving the students of an e-learning summer school the task of developing the model for a simple domain in under sixty minutes using ontology. Some students also used our tool to develop a complete tutor in around eight hours, which is much faster than they could be expected to author the system without the tool. The results suggest this style of authoring can lead to very rapid ITS development. We further extend the ontological approach with domain schema: high-level abstractions that describe the semantics of the domain model for a class of domains. Using domain schema reduces the authoring effort to one of describing only those aspects that are unique to this particular domain, and enables the ontology-based approach to model domains with different semantic requirements.