The aim of this paper is to approach and understand the parametric design as a procedure that is subject to rational steps. To look for the ability of this procedure to ensure the integrity of an architectural project and maybe the legitimation of it, while any attempt to design within a continuously changing information environment is confronted with the uncertainty of the final choice. There is questioning about the digital nature of parametric design and the changes that induces in the geometry and the relation between objects and space. Questioning about the strategy we use to associate the parameters with the components in a project. There is an attempt to survey the methods of construction that ensure the implementation of digital and feedback the design process. For a better understanding of the process, some case studies are examined and an attempt is made to parametrically design a shelter using Grasshopper plug in for Rhino design program.