Concurrent Reflective Abstract State Machines

The core of a distributed system can be characterised by autonomously acting agents, where each agent executes its own program, uses shared resources and communicates with the others, but otherwise is totally oblivious to the behaviour of the other agents. In a distributed adaptive system (DAS) agents may change their programs, enter or leave the collection at any time thereby changing the behaviour of the overall system. The behavioural theory of DAS provides an axiomatic definition plus a proof that concurrent reflective abstract state machines (crASMs) captures all systems stipulated by the axioms. In this paper we take a closer look into crASMs emphasising the tree background structure that is needed for handling the manipulation of self-representations.