The complexity of Embedded System (ES) development is increasing dramatically. This has several cumulative sources: the intricate combination of data-intensive, computational and control aspects; the ubiquity of parallelism and heterogeneity of modern architectures; and the diversity of target-specific, non-deterministic programming models (e.g., C++ with explicit message passing, OpenCL, VHDL). Model-Driven Engineering (MDE) proposes to manage complexity by raising the level of abstraction for designers and developers, and refining the implementation for a particular context and platform through model transformations. In such frameworks, behavior is often specified by means of Hierarchical State Machines (HSMs) equiped with an action language. However, although such models represent some level of control parallelism through objects and HSMs, data parallelism, compound data, and the exploitation and optimization thereof remains very limited. In this paper, we propose an action language that seamlessly combines HSMs with data parallelism and operations on compound data. It preserves the expressivity of HSM and captures a layout-neutral description of data organisation. It also extends message-passing with an intuitive semantics for this additional paralellism and provides strong foundation for array-based optimisation techniques. We present this language together with a baseline code generation flow to enable the production of efficient, low-level imperative code.