Learning Design (LD 2003) is a declarative language, meaning that it de-scribes what an implementation supporting LD must do. LD does not state how this should be done. Furthermore, LD is an expressive language, which means that it has the ability to express a learning design in a clear, natural, intuitive and concise way, closest to the original problem formulation. This expressiveness and declarative nature complicate the implementation of an engine that can interpret the specification. As a result, the main objective of this chapter will be to describe how such an engine can be implemented. We will provide guidelines which go beyond the published specification to help implementers incorporate LD into their products.