This paper presents structuring mechanisms for building executable specifications, in the field of interactive applications,
using the Interactive Cooperative Object formal description technique. The design life cycle of the specification is presented
as well as how PetShop (a software tool support the ICO formal description technique) can effectively support the various
phases of the life cycle. The concepts and the tool are presented on a Range Slider case study. The Range Slider is a medium
size component, used for instance, in the field of dynamic queries for information retrieval and visualisation.