Despite the continuous research to facilitate WSNs development, most safety analysis and mitigation efforts in concurrency are still left to developers, who must manage synchronization and shared memory explicitly. In this paper, we present a system language that ensures safe concurrency by handling threats at compile time, rather than at runtime. Based on the synchronous programming model, our design allows for a simple reasoning about concurrency that enables compile-time analysis resulting in deterministic and memory-safe programs. As a trade-off, our design imposes limitations on the language expressiveness, such as doing computationally-intensive operations and meeting hard realtime responsiveness. To show that the achieved expressiveness and responsiveness is sufficient for a wide range of WSN applications, we implement widespread network protocols and the CC2420 radio driver. The implementations show a reduction in source code size, with a penalty of memory increase below 10% in comparison to nesC. Overall, we ensure safety properties for programs relying on high-level control abstractions that also lead to concise and readable code.

C éU is a synchronous language targeting soft real-time systems. It is inspired by Esterel and has a simple semantics with fine-grain control over program execution. C éU uses an event-triggered notion of time that enables compile-time checks to detect conflicting concurrent statements, resulting in deterministic and concurrency-safe programs. We present the particularities of our design in comparison to Esterel, such as stack-based internal events, concurrency checks, safe integration with C, and first-class timers. We also present two implementation back ends: one aiming for resource efficiency and interoperability with C, and another as a virtual machine that allows remote reprogramming.

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Structured synchronous reactive programming (SSRP) augments classical structured programming (SP) with continuous interaction with the environment. We advocate SSRP as viable in multiple domains of reactive applications and propose a new abstraction mechanism for the synchronous language CÉU: Organisms extend objects with an execution body that composes multiple lines of execution to react to the environment independently. Compositions bring structured reasoning to concurrency and can better describe state machines typical of reactive applications. Organisms are subject to lexical scope and automatic memory management similar to stack-based allocation for local variables in SP. We show that this model does not require garbage collection or a free primitive in the language, eliminating memory leaks for organisms by design.

Terra is a system for programming wireless sensor network (WSN) applications. It combines the use of configurable virtual machines with a reactive scripting language that can be statically analyzed to avoid unbounded execution and memory conflicts. This approach allows the flexibility of remotely uploading code on motes to be combined with a set of guarantees for the programmer. The choice of the specific set of components in a virtual machine configuration defines the abstraction level seen by the application script. We describe a specific component library built for Terra, which we designed taking into account the functionality commonly needed in WSN applications—typically for sense and control. We also discuss the programming environment resulting from the combination of a statically analyzable scripting language with this library of components. Finally, we evaluate Terra by measuring its overhead in a basic application and discussing its use and cost in a typical monitoring WSN scenario.

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