# Multi-Purpose Ontology-Based Visualization of Spatio-Temporal Data: A Case Study on Silk Heritage
## 5 Results and Discussion
As can be seen, 6.3% of the objects that have information for location have multiple locations (usually because their production place is uncertain), whereas 8.9% of the objects that have time information have multiple time spans (usually because their dating falls into two different centuries). These types of uncertainty are not uncommon in CH. This fact has a direct impact in the SILKNOW implementation of STMaps. It might happen that a user wants to visualize objects that belong to a certain region. However, if some of them have multiple locations, they will be shown in all of them, making users \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Number of Objects** & & **Number of Objects** & \\  & **with “Production** & **\%** & **with “Production** & **\%** \\  & **Place” Information** & & **Time” Information** & \\ \hline Total & 36,081 & 100 & 29,465 & 100 \\ One value & 33,834 & 93.7 & 26,852 & 91.1 \\ More than one value & 2247 & 6.3 & 2613 & 8.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Number and percentages of objects with multiple locations and/or multiple time spans, included in ADASilk (on 21 December 2020). The total number of objects is 38,971. Figure 10: Example of objects with incomplete data, where: (**a**) results of a query in which some ring sections appear with light color; (**b**) depiction of the percentages for each property of an object; (**c**) detail of the object in (**b**). believe that there are more objects than actually are. An example is depicted in Figure 11. The user wants to depict on the map those records related to velvet in Venice (Venezia), Italy. In the current version of ADASilk, there are a total of 214 records that meet this criterion. When visualizing them in STMaps, the user sees 214 records in Venice, and 6 records in Italy (Figure 11a). Zooming in on the six objects (Figure 11b), it can be seen that the icon indicates that they have multiple locations and, inspecting them in detail (Figure 11c), it can be seen that the location description includes both Italy and Venice. Venice is in Italy, and one might think that it could be better to only show, in STMaps, the locations in Venice. However, the domain experts' advice is to show both locations, since in most cases, it will be unclear if an object belongs to, for instance, Venice or to another region of the same country, so the catalogue of the object needs to reflect both. That is the reason why we prefer to map the two locations (with a special icon warning about data uncertainty), and let the user explore them on the map. The objects in Figure 11 might also belong to different time spans. This can be checked when visualizing objects in different centuries, as shown in Figure 12. For instance, the sum of objects that are placed in Venice is 233, where it should be 214 if none of them belongs to multiple time spans. Therefore, there might be 233 \(-\) 214 = 19 objects with multiple time spans, in case that objects fall at a maximum of two centuries; this is the common case, e.g., an object can be dated from 1685 to 1710, so it will be mapped to the timelines belonging to both the 17 th and 18 th centuries. The result shown in Figure 12 enables a domain expert to explore the temporal evolution of velvet in the region of Venice. As can be seen, most of the objects were produced during the 18 th century. Figure 11: Example of objects that have multiple locations, where: (**a**) results of a query; (**b**) depiction of objects with multiple locations; and (**c**) details of one of the objects. Finally, in order to show the meaningfulness of STMaps in the context of the features provided by other related interactive maps, we have elaborated a small comparative table (Table 3) in which we classify other mapping solutions that are related to cultural heritage, history and/or collections of museums.