Three types of representation are typically produced during the User Interface (UI) development life cycle: a conceptual representation holding the models used for elaborating a UI, an internal representation concerning the code of the UI, and an external representation expressing the look and feel of the UI. While the end user typically manipulates the external representation only, the designer and the developer respectively focus on the conceptual and internal representations. The Comets Inspector gathers all three representations into a single environment, thus providing the user (actually, the designer and the developer; in the future, the end-user) with multiple views of a same UI simultaneously. Each representation is made observable and modifiable through one or many "mini-UIs". Consistency is ensured through mappings between these representations. From a methodological point of view, the benefit is the integration of three stakeholders' perspectives in a consensu...