Depending on the time of solving a received task the users are categorized in many categories. In the paper structures of time intervals are determined for establishing types of users and models to determinate the users’ collectivities according to the time needed for solving the users’ tasks.

Goods that compose the public propriety are affected by satisfy of public interest. Therefore, they need to be protected against all interferences and degradation that could compromise their affectation, a protection that covers various aspects. The first affair concerns the risks of material...