The core of authoring system consists of two applications called Lyssa and Nyx (Named after the Greek goddesses). The first program is responsible for the creation of bricks and their combination to higher structures. It stands for most of the functionality described by the construction kit metaphor. Nyx is very important for the translation process of the courses to the different layouts and media types but is not as covered as Lyssa by the metaphor. Therefore, the following text focuses on the functionality of Lyssa and the collaboration with Nyx.

Figure~2 illustrates the process of model creation.

a)	b)
Figure 1: The Process of model creation

An abstract view on the aggregation process is shown in a). Lyssa reads several bricks and aggregates them to one model. An important aspect of the definition is the recursive use of models. Not only bricks can be combined but also models. That allows an individual structure of the contents and leads to several possibilities of reuse. Now it is imaginable to create learning objects, structures, chapters etc. with less effort.

The process with internal structure details is shown in b). In this illustration a tree is used inside of Lyssa to arrange the different bricks and models but every other kind of relation, e.g. list and net, is conceivable. These different data structures influence the appearance and the sequencing of the same content. For this reason, Lyssa uses one independent list of all included bricks and allows the definition of several navigation paths.