This work is based on the Semiotic Engineering theory of Human-Computer Interaction. This theory views the application interface as a meta-communication act, a message from designer to user, representing the designers` view of the artifact he developed. Since the designer cannot be present in the interface, he is represented by his deputy, who is endowed with a communicative capacity that allows it to carry out a discourse that is complete and exclusively regarding the designers` final conclusions about the needs, preferences, capacities and opportunities that he understands the user has. Being impossible to predict all the interpretations that each user can generate for the application, the designer needs, through his deputy, to explain everything that he did (and why he did it), and to give the users a chance to clarify their doubts. The best alternative for metacommunication is, certainly, the help system. In this way, the work herein proposed extends the current theoretical model of Semiotic Engineering, making explicit the presence of the help system and its communicative role. The purpose of this extension is to provide software designers with epistemic tools to support them when constructing their application`s help systems. These tools allow designers to explore help systems` communicative power, supporting them in the reflection about the materials available for its elaboration (design models, design rationale, among others), thus supporting them both in the construction of the discourse embedded in the help system, and in the elaboration of the possible ways the user will be able to express himself within this discourse.