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The CBorg Mobile Multi Agent Systems

The CBorg Mobile Multi Agent Systems. An Overview. Werner Van Belle Karsten Verelst Theo D’Hondt Programming Technology Lab (PROG) Departement Computer Science (DINF) Vrije Universiteit Brussel (VUB). Mobile Multi Agent Systems. Application: interconnection of agents Wide Area Network

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The CBorg Mobile Multi Agent Systems

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  1. The CBorg Mobile Multi Agent Systems An Overview Werner Van Belle Karsten Verelst Theo D’Hondt Programming Technology Lab (PROG) Departement Computer Science (DINF) Vrije Universiteit Brussel (VUB)

  2. Mobile Multi Agent Systems • Application: interconnection of agents • Wide Area Network • Fine grained component structure • Frequent migration of components

  3. Mobile Multi Agent Systems • A Mobile Agent is an Active Autonomous Component • Able to Communicate with others • Able to Migrate to other ‘Agent Systems’ • The Agent system is the “Operating System” to support these components

  4. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  5. CBorg • Developed at PROG • Goal is to implement a light weight MMAS for research purposes • We try to achieve as much transparency as possible • Features • location transparency • strong migration • Based upon an interpreted language Pico

  6. CBorg • The Cborg appliation is the operating environment (the agent system) which runs on every participating computer. • Cborg takes care of • naming agents • routing and sending messages to agents • creating and destroying agents • executing agents concurrently • migrating agents

  7. Naming/ Agent Systems • Every agent system has a unique hierarchical name;eg. tecra and void.tecra • Hierarchical interconnection between agent systems forms a mobile multi agent infrastructure

  8. Naming/ Agents • Agentnames are based upon the name of the agent system and a freeform identifier. Eg: tecra/session1 tecra/nameserveragent Agent Names does NOT change whenever an agent migrates

  9. A CBorg Agent • Object Oriented • Own Code & Data Space • Single Threaded • Agents run concurrently • Can send messages to other agents • Can migrate to other agent systems • Written in PICO

  10. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  11. PICO/Standard Stuff • Definition • a:900 • a[10]:0 • a(a,b,c):display(a+b+c) • Assignment • a:=90 • a[67]:=89

  12. PICO/Eval -Apply a:b:20 ag:read(“a+b”) eval(ag) -> 40 f(a,b)::a+b f(1,2) -> 3 f@[1,2] -> 3

  13. PICO/Variable Arguments f@args:: {sum:0; for(I:1,I<=size(args), I:=I+1, sum:=sum+args[I]); sum} f(1,2,3) -> 6 f@[1,2,3,4] -> 10

  14. PICO/Call by Name a:50 delay(f())::f delayed:delay(display(a)) a:=600 delayed() : 600

  15. PICO/Objects { makePoi(x,y):: {move(X,Y) :: { x := X; y := Y }; area() :: 0; makeSqu(w) :: {widen(W) :: w := W; area() :: w^2; clone() }; clone() }; Point: makePoi(0,0); Square: Point.makeSqu(2); Square.area() --> 4

  16. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  17. CBorg/ Communication • “tecra/ses1” a:agent(“void.tecra/disc”); a.calculate([[1,2],[3,4]]); “void.tecra/disc” calculate(matrix)::display(matrix) - Automatic serialisation and deserialisation - Transparant routering - Connectionless

  18. CBorg/ Callbacks • “tecra/ses1” a:agent(“void.tecra/negate”); a.calculate([[1,2]],agentself()) -> void “void.tecra/negate” calculate(matrix,resultto):: resultto.display(negate(matrix)) - Asynchronous message passing - Queued at receiver side - Returns always void at sender side

  19. CBorg/ Serialisation “tecra/ses1” makepoint(x,y):: {show()::display(x+”:“+y); clone()} a:agent(“tecra/ses2”) p:makepoint(10,20) a.show(p) -> 10:20 “tecra/ses2” show(p)::p.show() - pass objects by reference - pass primitives by value

  20. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  21. Migration • Weak Migration • The agent can only migrate whenever the agent has stored its entire state in its objects • Cooperation from the agent is required • Code should be written in a special ‘state’-based manner

  22. Migration • Strong Migration • At any moment an agent can migrate to another place without any special requirements towards the agent • The agent doesn’t need to take special precautions when executing • The agent doesn’t have to ‘cooperate’ • Code mobility becomes useful

  23. Use of Migration (I)

  24. Use of Migration (II)

  25. Use of Migration (III) yahoo 1 My application 2 3 4 repository

  26. Use of Migration (III) yahoo 1 My application 2 3 4 repository

  27. CBorg/ Migration • CBorg supports the notion of strong migration. agentmove(place(“void.tecra”))

  28. CBorg/ Migration Fac(n):: { if(n\\1 = 0, agentmove(place(“tecra/ses1”)), agentmove(place(“void.tecra/ses1”))); if(n=1,1,n*Fac(n-1)) }

  29. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  30. CBorg/ Concurrency • Agent = single thread • Agents run concurrently • Agent queued incoming messages • Agent can synchronize with other agents and pass messages through this temporary channel • ** drawing plz **

  31. CBorg/ sync (I) • “tecra/ses1” a:agent(“void.tecra/negate”); sync(a,100) -> 100 “void.tecra/negate” a:agent(“tecra/ses1”); sync(a,100) -> 100 - both parties wait at the sync - after both arriving at the sync they continue

  32. CBorg/ sync (II) • “tecra/ses1” a:agent(“void.tecra/negate”); sync(a,[10,any]) -> [10,50] “void.tecra/negate” a:agent(“tecra/ses1”); sync(a,[any,50]) -> [10,50] - Simple unification upon value - keyword ‘any’ used as wildcard

  33. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • f -- creation • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  34. CBorg/ Creation/Killing • Interactive • Dynamic createagent(<object>,<name>) agentdie(agent) > - makes a deep copy of the <object> - super will not be copied

  35. CBorg/ Creation MakeStarter(name,to):: {go():: for(i:1;i<=size(to);i:=i+1; {agent:to[i]; agent.go()}); agentclone(clone(),name)} init:MakeStarter(“I”, [agent(“tecra/ses1”), agent(“tecra/ses2”)]) init -> remotedict(“tecra/I”) init.go()

  36. Overview • 1 -- The Agent System • a -- infrastructure • b -- the language (pico) • c -- communication • d -- migration • e -- concurrency management • 2 -- Demonstration • 3 -- Internals • 4 -- Future Work

  37. Demonstration • Examples • Cborg: multi threaded link • Cborg: single threaded link

  38. Overview • 1 -- The Agent System • 2 -- Demonstration • 3 -- Internals • a -- Naming and Routing • b -- Migration • 4 -- Future Work

  39. Routing Problem • Whenever an agent migrates its name changes Its name shouldn’t change butHow do we route messages ?

  40. Forwarding B D a Forward msg a C Send msg A b

  41. Migrate Send locationupdate Forwarding B D a Forward msg C Send msg a A b

  42. Forwarding • Pro: • easy implemented • logging is easy • Contra: • communication is slowed down • interacting agent clusters are slow when migrated

  43. Forwarding • Message send: 2T • time over network to reach home location • time over network to reach real location • Agent move: T + t • time over network to inform home location • time over network to migrate to new (nearby) position

  44. Notifying Partners E B a -> D D a a -> D C Send msg A ba->D

  45. Migrate Send LocationUpdates Notifying Partners E B a -> C D a -> C C a Send msg A ba->C

  46. Notifying Partners • Pro: • doesn’t require a special architecture • suitable for fine grained secure systems • Contra: • impossible to know all possible communication partners • enormous overhead with popular agents

  47. Notifying Partners • Message send: t • Time over network to reach (nearby) communication partner • Agent move: (C+1)t + [T] • Time needed to update all communication partners • Time needed to migrate to new position • [Time needed to update name server]

  48. Name Serving & Routing D b -> Aa -> C Fetch addr A C Send msg b a

  49. Send location update Migrate Name Serving & Routing D b -> Aa -> C a Fetch addr A C Send msg b

  50. Name Serving & Routing • Pro: • easy implemented • routing mechanism is independent of naming system • Contra: • name updates are slow • name lookups are slow

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