Are we talking the same language? Terminology (adapt, self-adapt, self-configure … ) is often inconsistent, ambiguous or misleading ! Need more-precise classification, based on criteria such as:- What is adapted: Externally visible behaviour,Internal configuration, Internal logic or semantics,Internal structure or architecture. Over what time-frame the adaptation is effected: Immediate, having a one-off effect, Short term, changes remain in force until policy instance terminates, Long-term, changes are persisted to future policy instances. Does adaptation have local or global effects: Local changes affect a single node or agent, Global changes are propagated to other nodes. Richard Anthony University of Greenwich SAACS-panel

A possible classification Adaptive: Immediate action effect; reaction to environmental or context. System adapts instantaneous behaviour, but not itself. Current state of Practice ? Self-Configuring: Internal configuration is changed. E.g. changing a threshold which subsequently impacts rule evaluation. Current state of Practice ? Self-Adapting: Internal logic or semantics are changed permanently. E.g. changing the priority, and/or execution order of rules. Limited by the flexibility of adaptation mechanisms, and foresight of developer. Adaptation effectively pre-programmed at a meta-level. Current state of the Art (research) ? Evolvable: New behaviour is ‘learnt’. E.g. a new rule or policy is devised and found to be superior to current setup and is thus incorporated automatically. The Holy Grail ? Richard Anthony University of Greenwich SAACS-panel

Complexity Tail-Chasing! Simpler solutions are often appropriate – Adaptive often is sufficient. Self-adaptive more sophisticated, can cope with more-complex environments. Need to avoid a self-defeating paradox: The autonomics / self-* field has arisen from the need to hide complexity. Some of the most impressive examples involve embedding AI, ANNs etc, ! Complex solutions to the complexity problem ! Complexity accompanied by Risk (convergence, instability, verification, confidence, development costs …). ► Self-stabilisation will increasingly dominate importance amongst the self-* properties as sophistication increases. Richard Anthony University of Greenwich SAACS-panel