occam-π

Abstract: Future systems will be too complex to design and implement explicitly. Instead, we will have to learn to engineer complex behaviours indirectly: through the discovery and application of local rules of behaviour, applied to simple process components, from which desired behaviours predictably emerge through dynamic interactions between massive numbers of instances. This paper describes a process-oriented architecture for fine-grained concurrent systems that enables experiments with such indirect engineering. Examples are presented showing the differing complex behaviours that can arise from minor (non-linear) adjustments to low-level parameters, the difficulties in suppressing the emergence of unwanted (bad) behaviour, the unexpected relationships between apparently unrelated physical phenomena (shown up by their separate emergence from the same primordial process swamp) and the ability to explore and engineer completely new physics (such as force fields) by their emergence from low-level process interactions whose mechanisms can only be imagined, but not built, at the current time.

Abstract: The success of the Arduino platform has made embedded programming widely accessible. The Arduino has seen many uses, for example in rapid prototyping, hobby projects, and in art installations. Arduino users are often not experienced embedded programmers however, and writing correct software for embedded devices can be challenging. This is especially true if the software needs to use interrupts in order to interface with attached devices. Insight and careful discipline are required to avoid introducing race hazards when using interrupt routines. Instead of programming the Arduino in C or C++ as is the custom, we propose using occam-π as a language as that can help the user manage the concurrency introduced when using interrupts and help in the creation of modular, well-designed programs. This paper will introduce the Arduino, the software that enables us to run occam-π on it, and a case study of an environmental sensor used in an Environmental Science course.

Abstract: This is a proposal for the formal verification of occam-π programs to be managed entirely within occam-π. The language is extended with qualifiers on types and processes (to indicate relevance for verification and/or execution) and assertions about refinement (including deadlock, livelock and determinism). The compiler abstracts a set of CSPm equations and assertions, delegates their analysis to the FDR2 model checker and reports back in terms related to the occam-π source. The rules for mapping the extended occam-π to CSPm are given. The full range of CSPm assertions is accessible, with no knowledge of CSP formalism required by the occam-π programmer. Programs are proved just by writing and compiling programs. A casestudy analysing a new (and elegant) solution to the Dining Philosophers problem is presented. Deadlock-freedom for colleges with any number of philosphers is established by verifying an induction argument (the base and induction steps). Finally, following guidelines laid down by Roscoe, the careful use of model compression is demonstrated to verify directly the deadlock-freedom of an occam-π college with 10 philosphers (in around 30 seconds). All we need is a universe large enough to contain the computer on which to run it.

Abstract: The Flying Gator is an unmanned aerial vehicle developed to support investigations regarding concurrent and parallel control for robotic and embedded systems. During ten weeks in the summer of 2010, we designed, built, and tested an airframe, control electronics, and a concurrent firmware capable of sustaining autonomous level flight. Ultimately, we hope to have a robust, open source control system capable of supporting interesting research questions exploring concurrency in real time systems as well as current issues in sustainable agriculture.