Propagation Networks, A flexible and expressive substrate for computation

The “concurrency problem” is a bogeyman of the field of computer science that has reached the point of being used to frighten children. The problem is usually stated equivalently to “How do we make computer languages that effectively describe concurrent systems?”, where “effectively” is taken to mean “without tripping over our own coattails”. This problem statement contains a hidden assumption. Indeed, the concurrency itself is not difficult in the least—the problem comes from trying to maintain the illusion that the events of a concurrent system occur in a particular chronological order.