EEL 5937 What makes an agent? EEL 5937 Multi Agent Systems Lotzi Bölöni

EEL 5937 Trivial agents A thermostat –Senses the environment –Acts on the environment –Has a goal directed behavior Unix daemons: e.g. xbiff Even for trivial agents, the agent methodology might prove useful Even for trivial agents, emerging properties might solve higher level problems.

EEL 5937 Non-trivial properties of agents Intelligent behavior –Planning –Learning Communication –With agents –With users: high level communication Social behavior Representing the environment –Ontologies Mobility Mutability

EEL 5937 Communication in agents

EEL 5937 Inter-agent communication: Messages Communication can be explicit or implicit –Explicit: through messages / signals –Implicit: through actions which mean something Agent systems prefer message based communication –Client-server systems prefer remote procedure call (RPC) –Equivalent, but flavor is different Agent communication languages: FIPA ACL, KQML Various XML favors

EEL 5937 But what does it mean? ACL’s present a richer set of communication primitives than RPC. Asynchronous vs. synchronous “Performatives” a.k.a. communicative acts –Publish-subscribe –Broadcast –Query-reply –Request action –Propose-accept/reject proposal

EEL 5937 What is an ontology? Answer is 42. But what was the question? Communicative acts are meaningless if the agents do not have the same understanding about the passed data. An ontology defines a common vocabulary for entities who need to share information in a domain. It includes machine-interpretable definitions of basic concepts in the domain and relations among them. –Entities: agents, researchers, experts etc.

EEL 5937 Ontology examples The Yahoo categorization of web sites Dewey decimal notation –Used in libraries since 1876 RDF – resource description framework and its extensions –DAML (DARPA Agent Markup Language) –OWL –A large number of frameworks: check Cyc (

EEL 5937 Mobility

EEL 5937 Mobility in the physical and virtual world Physical mobility –Ability to move a physical artifact with whom the agent is associated –The laws of the physical world always apply: »Conservation of matter (!) »The laws of movement and dynamics Virtual mobility: –Ability to move software from machine to machine –The laws of physical world does not apply: »Agents can move to remote locations without traversing intermediary locations »Agents might be duplicated as a failure of movement »There are no forces, speed, etc. Emulated physical worlds: games, etc –They have the freedom of the virtual world, but choose to live in a version of the physical

EEL 5937 Strong and weak mobility for software agents Mobility: ability to move an agent from a machine across (potentially) heterogeneous platforms Strong mobility: can move any time –Language or virtual machine support needed –Telescript, modified JVM’s such as NOMADS Weak mobility: can move at certain points during execution –Aglets, D’Agents (formerly AgentTcl), Jade, Bond etc.

EEL 5937 Why mobility? Moving the code to the data instead of the other way around Mobile devices might require mobile agents –Disconnected operation We will have a lot of hardware, but we want a single software to talk to (can server based systems do it?) Many systems developed, no commercial success as of yet…

EEL 5937 Mutability

EEL 5937 Why mutability? Some applications: –Mobile agents, while traversing heterogeneous platforms might need to adapt –Remotely building up monitoring agents Future: –Continuous updating of long-lived agents –Self-repair, self-debug –Genetic algorithms for agent design

EEL 5937 Bond and agent surgery Project started at Purdue, currently at UCF – Agent described by a data structure (multiplane state machine). Agent can be described with a language (Blueprint) which can also describe agent surgery Agent surgery: controlled modifications on a running (!) agent