# Chatbot-Based Natural Language Interfaces for Data Visualisation: A Scoping Review
## 4 Results
### Data Space  
We analysed all the research works in terms of the main characteristics involved in the **Data Space**; see Figure 6.  
Table 1 summarises the analysed research works describing the explored data through visualisation: movies, sports, coronavirus, finance and others. We found that 70% (14/20) of them used multidimensional _tabular_ data [39; 40; 64; 81; 82; 83; 85; 86; 87; 88; 89; 92], while some of them also included spatial data [39; 70; 90; 91]. Moreover, the table details the kind of data attributes each V-NLI supports (nominal, numerical, temporal, spatial). Six of the twenty visualisation systems used _complex data_. For instance, Ref. [80] has data related to software bundles and \begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**V-NLI**} & \multicolumn{4}{c}{**Visual Space**} \\ \cline{2-5}  & \multicolumn{2}{c}{**Visual Mapping**} & \multirow{2}{*}{
\begin{tabular}{c} **View** \\ **Classical** \\ \end{tabular} } \\ \hline  & \multicolumn{2}{c}{**Visualisation**} & \multicolumn{2}{c}{**Graphical**} & \multicolumn{2}{c}{**Visual Mapping**} \\  & \multicolumn{2}{c}{**Elements**} & \multicolumn{2}{c}{**Identification**} & \multicolumn{2}{c}{**Trans.**} \\ \hline ACUI [80] & Adv (Network) & Lines, Points & Fixed & Single \\ \hline Ava [81] & Basic (Line) & Lines & User-defined & Single \\ \hline Boomerang [82] & Basic (Bar, Scatter, Line) & Lines, Points & Rule-based & Multiple \\ \hline Chat2 VEs [83] & Basic (Bar, Scatter, Line, Box-plot) & Lines, Points, Bars & Intelligent & User-defined & Multiple \\ \hline ConVisQA [69] & Adv (Hierarchical stacked bar) & Bars & Fixed & Single \\ \hline Data@Hand [84] & Basic (Bar, Line) & Lines, Bars & Fixed & Multiple \\ \hline DataBreeze [85] & Basic (Dots) & Points & Fixed & Single \\ \hline Evizeon [39] & Basic (Bar, Scatter, Line, Map) & Lines, Points, Bars & Fixed \& Rule-based & Multiple \\ \hline FlowNL [70] & Adv (Flow) \& Basic (Bar, Map) & Lines, Bars & Fixed & Multiple \\ \hline GameBet [86] & Basic (Bar, Line, Table, Shot) & Lines, Points, Bars & Rule-based & Single \\ \hline GeCoAGgrnt [87] & Basic (Pie) & Pies & Fixed & Single \\ \hline InChorus [88] & Adv (Parallel) \& Basic (Bar, Scatter, Line) & Lines, Points, Bars & Rule-based \& User-defined & Single \\ \hline Iris [89] & Basic (Satter) & Points & User-defined & Single \\ \hline MVA [80] & Basic (Bar, Line, Map) & Lines, Points, Bars & Fixed & Multiple \\ \hline ONYX [91] & Basic (Bar, Scatter, Map) & Points, Bars & Fixed \& User-defined & Single \\ \hline Okbo [15] & Adv (Network) \& Basic (Bar) & Lines, Points, Bars & Fixed & Multiple \\ \hline Snowy [40] & Basic (Bar, Scatter, Line) & Lines, Points, Bars & Rule-based & Single \\ \hline Talk2 Data [64] & Basic (Bar, Scatter, Line, Pie, Area) & Lines, Points, Bars, Pies & Rule-based & Multiple \\ \hline TransVis [63] & Adv (Network) \& Basic (Line) & Lines, Points & Fixed & Multiple \\ \hline Valetto [92] & Basic (Scatter) & Points & Fixed & Single \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of V-NLIs in defined visualisation categories. Visualisation Category (Basic and Advanced), Graphical Elements (Lines, Points, Bars), Visual Mapping Identification (Fixed, User-defined, Rule-based and Intelligent), and View Transformation (Single and Multiple views). Figure 6: Data Space overview and the main characteristics of the data involved in the visualisation pipeline. services such as OSGi bundles, and [15] uses network data displaying the relationships between football players. Furthermore, Ref. [69] has hierarchical data that is collected from online conversations and [70] works with flow data such as hurricanes. Finally, Ref. [84] has sequential temporal data (e.g., sleep time during each night), and [63] has transient data which is a data type that is relevant to a time period; in this case, it is the quality of software services over time. Regarding the **Data Transformation** step, 10/20 V-NLIs used a kind of data transformation.