Lambda the Ultimate

Michel Ingham, Robert Ragno, and Brian Williams, A Reactive Model-based Programming Language for Robotic Space Explorers, Proceedings of the 6th International Symposium on Artificial Intelligence, Robotics and Automation in Space, Montreal, Canada, June 2001.

Model-based autonomous agents have emerged recently as vital technologies in the development of highly autonomous reactive systems, particularly in the aerospace domain. These agents utilize many automated reasoning capabilities, but are complicated to use because of the variety of languages employed for each capability. To address this problem, we introduce model-based programming, a novel approach to designing embedded software systems. In particular, we introduce the Reactive Model-based Programming Language (RMPL), which provides a framework for constraint-based modeling, as well as a suite of reactive programming constructs. To convey the expressiveness of RMPL, we show how it captures the main features of synchronous programming languages and advanced robotic execution languages.

Reactive programming has been discussed on LtU quite a bit in the past. Functional reactive programming, in particular, has got a lot of attention. But I don't think we've covered reactive model-based programming before. This is an interesting approach that combines constraint-based modeling with reactive programming, and compiles programs down to hierarchical constraint automata for execution. Whereas reactive languages like Esterel focus on manipulating signals, RMPL works by manipulating (potentially hidden) system states.

Peter A. H. Petersen has written two weblog posts on abstraction and security:

• Abstraction -- Friend or Foe?, and
• Abstraction and Trade-offs: The Devil You Know.

The points he makes echo a theme dear to my heart: abstractions offer the programmer compositionality of construction when creating their programs and systems, but that notion of compositionality does not match all of the properties one needs to ensure that a system is secure. Cf. slogan #2, from my story The irreducible physicality of security properties:
 Security is non-modular: Programming languages and software engineering practices can ensure that software possesses properties helpful to security, but the properties are only meaningful in the context of a strategy to ensure a computer system satisfies its security policy;

Postscript — Before someone mentions it, Joel Spolsky wrote something quite relevant: The Law of Leaky Abstractions