VIS is a software which analyses and evaluates the quality and the degree of interactivity between sites/portals and users.
VIS is a program which delimits sixteen qualitative parameters which correspond to the basic elements of the Web pages. It assigns percentage points to each parameter and aggregates the parameters into four blocks of different qualities known as functors (functor stands for the whole of more functions)  of interactivity.

Functor 1 describes the functionality and the architecture of the information, functor 2 the communicative power, functor 3 the readability, and functor 4 the aesthetic/interactive coherence.