We present in this section a synthesis giving an overall view of the information visualization field: its definition, its categories and criteria for the classification of the visualization system. We then present the different techniques of information visualization such as maps, trees and graphs. Finally, we describe the best known results visualization tools currently available on the web according to an appropriate classification.
Indeed, the domain of visualization techniques is a very rich area; different techniques can be applied according to the purpose and properties of the data itself. Similarly, several important factors related to ergonomics are also to be taken into account in choosing a visualization technique. Generally, a suitable visualization technique must, to the extent possible, meet the following requirements (Bouthier, 2004):
Have a global view: allows getting an idea of all the data;
Zoom: allows to access, in context, to a specific data;
Have a detailed view: allows access to all the details of a specific data;
See relationships: allows focusing on the relationships between the data and not regarding the data itself.