Abstract. Aspect-oriented programming languages usually are extensions of object-oriented ones, and their compilation target is usually the (virtual) machine model of the language they extend. While that model elegantly supports core object-oriented language mechanisms such as virtual method dispatch, it provides no direct support for core aspectoriented language mechanisms such as advice application. Hence, current implementations of aspect-oriented languages bring about insufficient and inelegant solutions. This paper introduces a lightweight, objectbased machine model for aspect-oriented languages based on objectoriented ones. It is centered around delegation and relies on a very dynamic notion of join points as loci of late-bound dispatch of functionality. The model is shown to naturally support an important number of aspect-oriented language mechanisms. Additionally, a formal semantics is presented as an extension to the object-based δ calculus.