: This paper examines the personalization of online training simulations which are a key modern approach in computer aided education. More specifically it focuses on the difficulties involved in authoring personalized training simulations. The composition of such systems is very difficult which has hampered their wide spread adoption [Joolingen, 03]. Presently adaptive training simulations can only be authored by programmers working closely with subject matter experts. One of the key ways for adaptive simulations to increase their popularity in online eLearning [Wade, 09] is to reduce the effort and technical skills required by authors in their development. We argue that personalized online simulations need to be composed by subject matter experts, inexpensively and quickly. This paper details the twin challenges in composing content for both educational simulations and personalization. It also describes ACTSim, a new and unique composition tool that supports the rapid development of p...