15. Device for calculating and encoding a score of semantic and spatial similarity between concepts of an ontology stored in hierarchically numbered trellis form, wherein said device comprises at least means of calculating and encoding a semantic and spatial similarity score by convergence relative to their common semantic characteristics respectively by separation according to their spatial distance for each concept with respect to a central concept, taken two-by-two.
15. Device for calculating and encoding a score of semantic and spatial similarity between concepts of an ontology stored in hierarchically numbered trellis form, wherein said device comprises at least means of calculating and encoding a semantic and spatial similarity score by convergence relative to their common semantic characteristics respectively by separation according to their spatial distance for each concept with respect to a central concept, taken two-by-two. 16. Device according to claim 15 , wherein said device also comprises: means of discriminating special subhierarchies, of which the depth of each of the concepts is less than a determined maximum special subhierarchy depth value and of which the number of child concepts for one of each of these concepts is less than a determined maximum special subhierarchy width value; means of renumbering said concepts, said renumbering consisting in prefixing any identifier of a concept belonging to a special subhierarchy with the smallest positive integer number not yet assigned to the concepts of the hierarchy of concepts.