Architectural modeling is becoming a central problem for large, complex systems. With the advent of new technologies and user-centered concerns, the user interface portion of interactive systems is becoming increasingly large and complex. This chapter is a reflection on software architecture modeling for interactive systems. In this domain, a number of architectural frameworks have emerged as canonical references. Although these models provide useful insights about how to partition and organize interactive systems, they do not always address important problems identified by main stream software architecture modeling. We first introduce the notion of software architecture and make explicit the steps and issues that architectural design involves and that most software designers tend to blend in a rather fuzzy way. Building on general concepts, a comparative analysis of the most significant refernce models developed for interactive systems is then presented: the Seeheim and Arch models followed by the more recent agent-based approaches that can be shaped to support multimodal interaction and groupware.