Over the last decades, the practice of representing digital signal processing applications with formal Models of Computation (MoCs) has developed. Formal MoCs are used to study application properties (liveness, schedulability, parallelism...) at a high level, often before implementation details are known. Formal MoCs also serve as an input for Design Space Exploration (DSE) that evaluates the consequences of software and hardware decisions on the final system. The development of formal MoCs is fostered by the design of increasingly complex applications requiring early estimates on a system's functional behavior. On the architectural side of digital signal processing system development, heterogeneous systems are becoming ever more complex. Languages and models exist to formalize performance-related information of a hardware system. They most of the time represent the topology of the system in terms of interconnected components and focus on time performance. However, the body of work on what we will call Models of Architecture (MoAs) in this chapter is much more limited and less neatly delineated than the one on MoCs. This chapter proposes and argues a definition for the concept of an MoA and gives an overview of architecture models and languages that draw near the MoA concept.