SystemC is emerging as a de-facto standard for system design but it still lacks support for continuous-time models of computation and multi-domain systems. This becomes an issue as the systems under consideration are often heterogeneous. An effort has recently started to allow the SystemC framework to address this need by the definition of the so-called SystemC-AMS (Analog and Mixed-Signal) extensions. This paper defines the context of the extensions with respect to requirements and inferred design objectives. It also gives a rationale for each design objective. Finally, it presents preliminary seed works that will influence the development of the SystemCAMS extensions and provides some information on the next steps.