Even when we are careful to only use and create useful and relevant data, a GIS project rapidly contains a large number of layers, created especially during the intermediate steps of the analyses. In addition, the diversity of data that can be potentially used (raster, vector, tabular) means we must really reflect on how they are stored. It is equally essential to distinguish the original data (which may be subject to different authors’ rights) from data produced under the project. When working with regular files, not in a spatial-DBMS, we must reflect on the organization of the storage directory before embarking on treatment. Once the original data are stored in the files, one should avoid modifying them. Finally, it is often useful to organize layers into thematic groups. For example, you can keep together all the layers that concern the administrative limits in one group, and those describing the transport network in another.
See: Files (project), Data organization
[French: Fichiers (Gestion)