## 3 The Solution Proposed: WikiGIS
### WikiGIS Interface  
The website consists of a homepage displaying the workspace, and of a login/registration page for users (Figure 1). Most of the homepage consists of a Google Maps base map [1], a commentary field [8] and traditional browsing tools. Two modes are available [2]: a view mode (default selection) and an editing mode. \begin{table}
\begin{tabular}{|c|l|l|} \hline \multicolumn{1}{|c|}{Infletors} & \multicolumn{1}{c|}{WITS} & \multicolumn{1}{c|}{WIRGIS} \\ \hline \multicolumn{1}{|c|}{Data access} & \multicolumn{1}{c|}{Web server (Apache)} & \multicolumn{1}{c|}{Web server (http)} \\ \hline \multicolumn{1}{|c|}{Storage} & \multicolumn{1}{c|}{MySQL\_Oracle} & \multicolumn{1}{c|}{Spatial DB (MySQL\_Oracle)} \\ \hline \multicolumn{1}{|c|}{Formatting pages} & Simple markup language & \multicolumn{1}{c|}{GML, MWX: formats allowing both description of geographic data and their transfer on the Web} \\ \hline \multicolumn{1}{|c|}{Type of edition} & Asynchronous & Synchronous, redlining type \\ \hline \multicolumn{1}{|c|}{Types of data} & Text, image, sound, video & \multicolumn{1}{c|}{Geometric data (point, line, polyline, polygon), descriptive and graphic data} \\ \hline \multicolumn{1}{|c|}{Decoding the information} & Minimal & \multicolumn{1}{c|}{More complex} \\ \hline \multicolumn{1}{|c|}{Display of data} & HTML & \multicolumn{1}{c|}{- Geometric data: AJAX} \\ \multicolumn{1}{|c|}{} & \multicolumn{1}{c|}{- Descriptive data: HTML} \\ \hline \multicolumn{1}{|c|}{Historicity management} & Wiki browser & \multicolumn{1}{c|}{- Descriptive data: by wiki syntax (wiki browser)} \\ \multicolumn{1}{|c|}{} & \multicolumn{1}{c|}{- Geometric data: by file, indexation, spatial DB} \\ \hline \end{tabular}
\end{table} 
Table 1: Characteristics of the WikiGIS. The **view mode** is available by default for all users. It allows viewing of all of the geometric entities (points, polylines, polygons) with their related comments that compose the map at a given time chosen by the user (the logon date by default). The map can be explored by using the navigation tools [3], the zoom and pan controls [4] or by choosing an address, a place [5]. Two display types are available: visualization of the last updated geometry, and visualization of the history of the geometric shapes. The visualization of the last updated geometry is selected by default when the homepage is loaded. In this arrangement, the map displays the last update of each object. The visualization of the history of the geometric shapes is achieved in three different possible ways:  
* Through the consultation of a situation status at a given time (\(t\)) [6];
* Through the consultation of the advancement of a situation between two given times (\(t_{1}\)) and (\(t_{2}\)) via a linear temporal slider [7];
* Through the consultation of the descriptive information and of the history of a selected item [8]. The visualization of descriptive data is launched by clicking an object. Then, the corresponding information appears in a text box on the right of the map [8]. Descriptive data are arranged in two sets: the descriptive data associated with the last updated geometry object, and the descriptive data associated with former versions of the geometry object (each version being considered in the database as different temporal instances of the same object, and not as different objects). These text data include the author's identification and the creation date of the geometry, as well as the titles and comments associated with this geometry. The date of creation is one of the structural elements of the geographical data management in the Wiki. This date is actually the date of the registration of the transaction in the database. Transaction is defined here as any action done by a user in order to create a new object; or to change one or more components of an existing object (e.g., changing location, changing its shape,  
Figure 1: WikiGIS Interface. appearance or descriptive associated data); or to remove an existing object.