The design of interactive systems is a complex, iterative and collaborative process, composed of different activities that are interrelated in the composition of a final product and requires different expertise to perform it. The information produced during each activity is very important for the continuity of the process and to understand, explain and maintain the product produced. This information must be related and integrated in a clear and coherent speech, allowing traceability and addressing the origin and the context in which they were produced. It is noted, however, that the proposed process catch and modeling in HCI design provide a fragmented and/or incomplete view of this process. For this reason, we propose an epistemic model, based on Design Rationale (DR), suitable for the recording and modeling of the design of interactive systems. Based on the review and analysis of the key views and proposals of the design process, their requirements, models, notations and support languages, the epistemic model Ideia has been proposed. The model has as its main goal to register and report design activities in a cohesive manner, offering support for the reflection of the design team about the activities of the design process as well as information sources for the traceability of information. For this, the model proposes the integration of inputs and outputs (e.g., requirements, models, artifacts) of the activities of analysis (problem space) and the conceptual design (solution space) DR. The model was implemented in the Deprost prototype and adopted in the design of part of the WikiMapps project, allowing us to evaluate the proposal in a real case study.