This article begins with a summary of two dominant approaches to adaptive learning systems: Intelligent Tutoring Systems (ITS), which have been around since the late 1970s and relatively new learning systems based on Learning Analytics, deriving largely from technical advances in BIG DATA pioneered by Google. The article then describes a third approach deriving from a long history of basic research in structural learning. TutorIT is a dynamically adaptive tutoring (not just adaptive learning) system that interacts with students based on what they do and do not know at each point in time -- as might a good human tutor. AuthorIT is an authoring platform that makes it possible for subject matters experts and instructional designers (SMEs) to create dynamically adaptive tutors in their own areas of expertise.