The involvement of users in system development (End user development) has attracted significant attention in the last ten years, given that users can adjust the applications according to their desires and needs. TheWeb 2.0 has now made possible the development of a new culture of user participation through social networks, where users share knowledge, experience and abilities. The contribution of this research is to provide knowledge and tools to foster a culture of participation among end users in the process of software development. One of the social contexts where such participation is particularly important is that of group systems, where changes desired by some typically affect other users in ways that may not always be desirable for all. Our main contribution is a model founded in Semiotic Engineering to support describing and negotiating system evolution in group discussions. Its main features are: (i) it provides a structure for the communication between people involved in the negotiation, and (ii) it combines three representational systems (interface language, natural language used in annotations, and a script language for interaction in Web pages). These languages are combined into a hybrid specification language for end users. We implemented feature (ii) through the tool primoTiWIM (This is What I Mean). We focused on the implementation and evaluation of feature (ii), since expression through this combined language affects the communication quality of the whole process that we wish to support. In order to evaluate our proposal we carried out empirical studies in which we sought to observe the first reactions and impressions of users in face of the primoTiWIM Tool. We concluded that the proposed model has the potential to promote a culture of participation in the context of the co-authorship between user-eveloper and software developers.