Virtual Reality Full Immersion Techniques for Enhancing Workers Performance, 20 years Later: A Review and a Reformulation <s> B. 2D, 3D and RV Viewing Modes <s> Since the emergence of databases in the 1960s, the volume of stored information has grown exponentially every year (Keim (2002)). This information accumulation in databases has motivated the development of a new research field: Knowledge Discovery in Databases (KDD) (Frawley et al. (1992)) which is commonly defined as the extraction of potentially useful knowledge from data. The KDD process is commonly defined in three stages: pre-processing, Data Mining (DM), and post-processing (Figure 1). At the output of the DM process (post-processing), the decision-maker must evaluate the results and select what is interesting. This task can be improved considerably with visual representations by taking advantage of human capabilities for 3D perception and spatial cognition. Visual representations can allow rapid information recognition and show complex ideas with clarity and efficacy (Card et al. (1999)). In everyday life, we interact with various information media which present us with facts and opinions based on knowledge extracted from data. It is common to communicate such facts and opinions in a virtual form, preferably interactive. For example, when watching weather forecast programs on TV, the icons of a landscape with clouds, rain and sun, allow us to quickly build a picture about the weather forecast. Such a picture is sufficient when we watch the weather forecast, but professional decision-making is a rather different situation. In professional situations, the decision-maker is overwhelmed by the DM algorithm results. Representing these results as static images limits the usefulness of their visualization. This explains why the decision-maker needs to be able to interact with the data representation in order to find relevant knowledge. Visual Data Mining (VDM), presented by Beilken & Spenke (1999) as an interactive visual methodology "to help a user to get a feeling for the data, to detect interesting knowledge, and to gain a deep visual understanding of the data set", can facilitate knowledge discovery in data. <s> BIB001 </s> Virtual Reality Full Immersion Techniques for Enhancing Workers Performance, 20 years Later: A Review and a Reformulation <s> B. 2D, 3D and RV Viewing Modes <s> The question whether to use 2D or 3D for data visualization is generally difficult to decide. Two-dimensional and three-dimensional visualization techniques exhibit different advantages and disadvantages related to various perceptual and technical aspects such as occlusion, clutter, distortion, or scalability. To facilitate problem understanding and comparison of existing visualization techniques with regard to these aspects, this report introduces a systematization based on presentation characteristics. It enables a categorization with respect to combinations of static 2D and 3D presentations of attributes and their spatial reference. Further, it complements existing systematizations of data in an effort to formalize a common terminology and theoretical framework for this problem domain. We demonstrate our approach by reviewing different visualization techniques of spatial data according to the presented systematization. <s> BIB002
For Zohra BIB001 , there are different approaches to the use of 2D, 3D and RV representations in relation to the Visualization of Information, presenting a brief description of each: • 2D uses only two dimensions; the graphics are flat, it stands out for its simplicity, clarity and precision when displaying information. A large part of the actual interfaces are designed for this type of representation. In most, the interaction is traditional, using the most common interaction techniques such as: Select and Zoom. • 3D, is the way in which an object is represented in a three-dimensional space, mapped on a twodimensional surface. The visual perception of 3D it is achieved through the use of visual elements of depth such as lights, shadows and perspectives, but the final appreciation is flat. These environments facilitate navigation, however, they result only from an extension of the interaction techniques in 2D environments, which use visual effects to generate the illusion of volume. • VR is a technique that enables immersion in a multimodal viewing environment, which also uses stereoscopic images to improve depth perception, making possible to perceive 3D as in the real world. VR environments allow the user to be immersed, causing the interaction to be different. Unlike the visualization techniques in 2D and 3D, VR techniques have not been thoroughly studied or standardized. An example of VR interaction techniques is: Direct manipulation, in which a virtual hand is available to interact directly with the visualization. Between 60% and 80% of the objects of study to be viewed are of 3D, but most of the visual representations implemented are in 2D, followed by those made in 3D, because those conceived in VR are currently very scarce  . The debate regarding the quality between 2D and 3D is still extensive, but many authors reach the consensus that 2D are the most appropriate if accuracy and better interpretation are desired; instead, 3D are useful if better navigation and relative positioning are preferred BIB002 . Fig. 1 shows an example of the three types of environments. 