A database is a structured set of information stored on a computer system, designed and built for consultation. Modifications are easy, fast and safe, even by many concurrent users. A database is made up of building blocks of homogeneous data grouped as records corresponding to entities of the same nature. These blocks are associated with logical or geometric relationships. There are several database technologies. The most common now is that based on the relational model where the data is organized in tables, and where the lines have different occurrences of the entity (the different plots of land entities for example) and the columns have attributes of this entity (the surface of the land, for example).