## 3 Results
### Identifying the Chain of Commands Used
#### 3.2.1 Wizard of Oz Experiment  
In a Wizard of Oz [39] experiment, users interact with a simulated system, the name of which comes from the novel in which a human hidden behind a screen creates the effect of something that does not exist. In this case, a system was simulated to perfectly interpret the users' natural language and perform the required actions on the GIS, as the user's screen was connected to the wizard's computer. The \"wizard\", who was in the same room, hidden behind a wall, could hear what the user was saying (Figure 7). The experiment was carried out by three researchers, who rotated among two predetermined roles: the interviewer and the wizard. The former greeted users at the door, explained the general objective of the test, and led the user to the test station adjacent to the wizard's hideout. Then, they observed the test performance and took field notes, without interfering with the user-system interaction. Figure 6: Requests to change layer functionality. As shown in Table 2, four scenarios were designed for the users to run through all the typical map interaction functionalities. These scenarios naturally integrated various necessities of functionality but also induced errors to observe the full range of user behavior in different situations. For each scenario, a list of predicted errors and a set of search terms were developed to allow the wizard to react to users with enough speed to be convincing. For this purpose, strategies were specified to mask the use of peripherals and sound, all to maintain the illusion and thus elicit natural reactions from the users. A brief satisfaction interview followed (asking about difficulties observed during the test, their perceptions, and other emerging issues) and an anonymized user profile survey. Then, the deception was revealed, and we offered users the option for us to remove the recording of the experiment from our study if they wanted. Finally, we spoke with each user to ascertain their reactions to understanding the whole experiment. In selecting users, we sought to achieve diversity in the factors relevant to interacting with systems by voice (e.g., age, experience with computer systems, dialect variety, and level of education). Because of the qualitative character of the methodology, along with the relatively small sample, each recording was studied in detail. Each functionality \begin{table}
\begin{tabular}{c c c} \hline \hline
**Scenario Description** & **Planned Errors** & **Planned Searches for the Wizard** \\ \hline Your Aunt [PERSON] is on a business trip to Sri & & \\ Lanka and you would like to know about the island. Locate the island and research the capital city (Colombo) and national parks. & & \\ \hline You are looking for a park in Paris to have a & If you look for _parque Paris_ (Paris \\ picnic. It is summer, and you want a place & & \\ with plenty of trees and shade. Compare the & & \\ leafiness of the parks using satellite images. & & \\ \hline You have an appointment with a friend on & & \\ the first roundabout of the city of Vitoria & & \\ (Spain), arriving via highway A-132. Look for & & \\ this point on the map to learn how & & \\ to get there. & The command _rotonda A-132_ shows & \\  & only the road. & \\ \hline You have to carry a package from the & & \\ Grancasa shopping center in Zaragoza to & & \\ Pilar Square. Find the pedestrian route & & \\ without using the routing functionality & & \\ provided by Google Maps. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Wizard of Oz Scenarios, Predicted Errors, and Error Mitigation. Figure 7: Configuration of the scenario for the Wizard of Oz experiment (figure from the authors, designed using resources from [40]). that the user tried to engage, and whether the wizard could respond to the request or not, was recorded to determine the optimal form of natural interaction on which to base the prototype. The main goal of this experiment was to observe the strategy the users employed to solve the problems presented.