# Mathematical description¶

In this Section the **mathematical description** of a model generated by urbs
will be explained. The structure here follows the basic code structure and
proceeds as follows:

First, a short introduction into the type of optimization problem solvable with urbs is given. This is followed by the description of the minimal possible model in urbs. As a next step the two main expansions of models, which also increase the index depth of all variables and parameters are discussed in the parts ‘Intertemporal modeling’ and ‘Multinode modeling’. The description is then concluded by the additional description of various feature modules. The latter are discussed in full index depth, i.e., with all features introduced in minimal, intertemporal and multinode modeling.