Résumé
For over thirty years the database SOPHY characterizes, numerically, the socio-ecological behavior of plants and defines the environment of all his relevés by their fidelities, raw or average ones, in respect of more than 8.000 indices of variables. Plants characterize not only the relevés but they are also considered as indices of variables. The fidelity of a plant at each of its co-occurring plants is the probability that the appropriate environment for these co-occurring plants can also be appropriated for the considered plant. One of the goals of SOPHY is to reestablish phytosociology on stable digital bases starting from the relevés themselves. However, to circumvent the impossibility to classify 200.000 records, it is necessary to proceed gradually, by carrying at each step more order and precision. The first step is to create clusters of relevés as ecologically similar as possible using a geographical algorithm combined with a classification algorithm based on 1.000 records at once. This step produced 3.945 cores of relevés, each core containing between 1 and around 250 localized relevés. The second step classifies 3.945 cores and produces a higher hierarchy of the main environments for plants in France. The types of environments obtained are 276 and they are now called Mesotypes. Each one is characterized by its particular components that are geographical and altitudinal parameters, constitutive and discriminant plants. The third step assigns Mesotypes to these relevés, whether they are localized or not and whether they have already been taken into account in the first step or not. Relevés are thus affected to their most ecologically similar Mesotype. They are considered as isolated clusters, clusters which are then separated as they have between 5.000 and 15.000 records. Twenty of these clusters are thus produced. The fourth step classifies and then successively, manages records of the twenty obtained clusters. These results are complemented by links which allow finding at what classification and at what level of the hierarchy each relevé belongs to.