# SINDVis: User-Centered Dynamic Interactive Visualization System for Space Information Networks
## 3 Theory and Methods
### SINDVis Architecture  
The main purpose of visualization technologies is to satisfy users' visual experience, and to realize the requirements of data analysis based on visual views. Network dynamic visualization is no exception. Therefore, we think that the SINDVis framework should include dynamic data input, visual view generation, visual view output, and users. Based on this, we designed the SINDVis framework as shown in Figure 5. \begin{table}
\begin{tabular}{c c c} \hline \hline
**User Class** & **GeoView** & **TopolView** \\ \hline USE-1 & \(\bigstar\bigstar\) & \(\bigstar\) \\ USE-2 & \(\bigstar\bigstar\) & \(\bigstar\bigstar\bigstar\) \\ USE-3 & \(\bigstar\bigstar\) & \(\bigstar\bigstar\bigstar\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Degree of requirement of multi-class users. As shown in Figure 5, the SINDVis framework was constructed from a dataset (input module), a visual method set (core-processing module), a view set (output module), and a user body. To demonstrate the SINDVis architecture more clearly, we analyzed its composition in more detail, as shown below. * **Dataset**: The dataset is an input module for SINDVis, consisting of an entity dataset and a network dataset, and the network data in topology domain is mapped from the entity data in the entity domain. The entity dataset consists of space data, such as satellite orbital parameters, satellite operating satellite cycles, satellite coverage, data transfer between satellites, etc. By mapping space entities to nodes and by mapping relationships between entities as edges, we formed the network dataset. Both of the above provide input to the SINDVis. * **Visual method set**: The visual method set is a core-processing module of SINDVis and it includes the entity domain methods and topology domain methods. For the entity domain, we refer to the visual views of STK and SaVi and realize the dynamic display of the structure and running state of the SIN in the entity domain. For the topology domain, we realize the dynamic display of evolution laws of the SIN topology structure. The visual method set is a large collection of methods, and the essence of the visual method set is a black box. The implementation methods of the entity domain mainly include visualization and interaction methods. The implementation methods of the topology domain mainly include layout, visualization and interaction methods. Because of the different principles and different objects of the entity domain and topology domain, the implementation methods of each are also different. * **View set**: The view set is the output module of the SINDVis, including the entity domain view, named GeoView, and the topology domain view, named TopolView. As we know, the visual view is a direct embodiment of the implementation of visualization technologies, and it is also a medium for showing information and implementing user interactions. Meanwhile, we think of the visual method set as processing, and the view set as results. Therefore, we constructed the visual method set and the view set separately. In SINDVis, the GeoView and TopolView appear on different pages at the same time. Of course, the specific display forms of the GeoView and TopolView depend on the specific visual methods selected. Meanwhile, the view set can feed the user's new requirements into the input module and the core-processing module, thus generating output modules that meet users' new requirements. Figure 5: SINDVis architecture. * **Users**: Users are the center of the SINDVis, and users' requirements are the basis reference for SINDVis function settings. Visual interaction is built between the view set and users. Meanwhile, the users enable real-time interaction with the view, and the users can control the views in real-time. Because the SINDVis is a dynamic visualization system, the main interaction is the time control of users. In addition, due to the limitations of page size, users can zoom in, zoom out, or pan the views according to their own interests.