Resilience through Dynamic Reconfigurations in Agent Systems Ilya Lopatkin Newcastle University, School of Computing Science

Multi-Agent System (MAS)‏ Agent Resource 2 Active agents Resources Communication

Multi-Agent System (MAS)‏ Agent 3 Active agents Passive agents Communication Agent

Threats and reconfiguration in MAS Questions concerned:  how to find appropriate components to use after failures?  which of them to choose? 4 Agent  Agent is unavailable  Abnormal behaviour  Disconnection  Inadequate quality of data  Inadequate QoS  Lack of required characteristics ? ? ? ? ? ?

Search mechanism The place of the search mechanism in FT 5 Damage confinement and assessment Error recovery Fault treatment and continued service Error detection * T. Anderson, P. A. Lee. Fault Tolerance: Principles and Practice. Prentice Hall, London, 1981

Scope of work 6 Searcher Criteria  Location addresses  Request List of locations Error detection Search Reconfiguration

Device Platform Location Agent Middleware Agent Middleware Agent Middleware CAMA abstractions 7

Agent Evaluation of locations Location Value* Searcher 8 evaluates produces * G. Di Marzo Serugendo, J. Fitzgerald, A. Romanovsky, and N. Guelfi. A Metadata-Based Architectural Model for Dynamically Resilient Systems. In 22nd ACM Symposium on Applied Computing, Seoul, Korea, March , pp ACM, 2007.

Sharing values among agents Location 1 Location 2 Value A2 Agent B Agent A Criterion Value A2 9 uses reads from saves to evaluates uses

Aggregating values Location 1 Location 2 Value Q2 Value P2 Agent A Value PQ2 contains Location 3 10 saves PQ2 contains reads Q2 reads P2 aggregates into

Criteria Application-specific Evaluate, aggregate, and compare values May include any resilience criterion Examples: Availability. Value: estimated time per week/month/year Connection properties, latency. Value: average time in ms Number of failures. Value: integer Quality of service. Value: some complex structure 11

Threats and reconfiguration in MAS Questions concerned:  how to find appropriate components to use after failures?  which of them to choose? 12 Agent  Agent is unavailable  Abnormal behaviour  Disconnection  Inadequate quality of data  Inadequate quality of service  Lack of required characteristics ? ? ? ? ? ? meta-data

Advantages Works for any type of components Leads to Any resilience criteria Autonomous agents High scalability 13

Problems First wave of agents Too many locations Lack of values Different treatment of the same values Need for a general ontology to represent values Hidden stigmergy may lead to unpredictable behaviour 14

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