IIKC database structure. The four hierarchical levels are represented by grey circles and are numbered 1 to 4 (black). The first level gathered the 23 descriptors available at the start of identification. Descriptor logical dependency between two descriptors was shown by a black line meaning a particular state of the descriptor into level n have to be selected to “unlock” the one into the level n + 1. The unlocked descriptors were incremented in the list of the descriptors available to user.