## 4 Results and Discussion
### Course Design: Visual Creation and Exploration of Course Contents  
The second use case is concerned with the visual creation of a compound graph using the multiscale visualization framework proposed in this paper. This will be done by illustrating the design process of a course, specifically the \"Computer Structure\" course within the \"Computer Science\" degree program at Universidad Rey Juan Carlos in Madrid. The planning of a course is an iterative process consisting of several phases. One of them is the structuring and sequencing of the contents, which is usually done using generic tools such as word processors or spreadsheets. A top-down approach is commonly followed in which the content is initially structured in large blocks or modules and then subdivided into finer levels of granularity. After defining the content to be taught, it will be necessary to sequence and make a temporal planning of the activities, assigning time slots to each one of them. In the context of this use case, Carbonic supports the visual creation of the hierarchical structure of the course, also allowing the insertion and visualization of the dependency relationships between concepts, something that is typically in the mind of the teacher who is designing the course but is not commonly depicted in the course plans. The creation of meta-nodes to represent the modules and their subdivisions can be done interactively through the context menu that appears when clicking with the mouse on the empty canvas displayed when launching Carbonic. However, prior formalization of the working domain will allow establishing the elements permitted at each level of the hierarchy as well as their attributes. This formalization (available at [[https://vg-lab.es/carbonic/course-domain.djson](https://vg-lab.es/carbonic/course-domain.djson)]([https://vg-lab.es/carbonic/course-domain.djson](https://vg-lab.es/carbonic/course-domain.djson)), accessed on 10 June 2022) will guide the process of creating entities and relationships, avoiding the generation of erroneous elements according to each level of the hierarchy. In addition, as explained in Section 3.2, the definition of which attributes can have each type of entity and their types allows the creation of appropriate filtering widgets for them. In this example, the contents have been structured in four hierarchical levels: _modules, units, lessons_, and _concepts_. Concepts have two attributes: their relevance according to the teacher's judgment and their duration, which reflects the time spent working on the concept in a session. In addition, the dependencies across concepts are formalized as directed adjacency relations, reflecting that the target concept depends on the source concept. Figure 18 shows the course structure modeled using a traditional textual scheme. The creation of this hierarchical structure comprising the contents of the subject will be easily carried out through Carbonic's graphical interface, simply by right-clicking the mouse and selecting the option to create children from the contextual menu (Figure 19). Afterward, each node can be edited by right-clicking on it to set the appropriate values of its attributes, previously specified in the domain file. The result is shown in Figure 20, where the same structure created with Carbonic is depicted. Finally, adjacency relationships can be created by selecting the source and destination via a mouse click. For the sake of simplicity, only the dependencies between concepts of different units have been created, ignoring those between concepts of the same lesson or of the same unit. Figure 20 shows the final result, where the contents distribution and the dependency among them can be simultaneously observed. It is easy to notice that Module 4 does not present any previous dependencies, which indicates that it could be moved and taught at any time during the course and even assessed whether those concepts could be moved to a different course.