1. Agents & Mobile Agents

2. Agents
An agent is anything that can be viewed as perceiving its environment through sensors and acting upon that environment through actuators
Human agent: eyes, ears, and other organs for sensors; hands,
legs, mouth, and other body parts for actuators
Robotic agent: cameras and infrared range finders for sensors;
various motors for actuators

3. Agents and environments
The agent function maps from percept histories to actions:
[f: P*  A]
The agent program runs on the physical architecture to produce f
agent = architecture + program

4. Vacuum-cleaner world Percepts: location and contents, e.g., [A,Dirty]
Actions: Left, Right, Suck, NoOp

5. Agents - what are they?

6. Objects and Agents – An Analogy
Objects encapsulate state, Agents encapsulate state + execution behaviour
Objects have no control over the execution of methods
Invocation of method m on object o – involuntary – whether object o likes it or not

7. Objects and Agents – An Analogy
Agents have control of whether or not to perform any given action
Request actions rather than invoke methods

8. Microsoft Agent
persons Microsoft Agent

9. Basic Definitions

10. Rational agents
An agent should strive to "do the right thing", based on what it can perceive and the actions it can perform. The right action is the one that will cause the agent to be most successful
Performance measure: An objective criterion for success of an agent's behavior
E.g., performance measure of a vacuum-cleaner agent could be amount of dirt cleaned up, amount of time taken, amount of electricity consumed, amount of noise generated, etc.

11. Simple reflex agents

12. Agents - Applications many due to:
agent research spans disciplines: artificial intelligence, distributed computing, software engineering (ABSE), sociology, psychology, economics, object-oriented systems, artificial life, game theory, ...
a sampling... 12

13. What is a Mobile Agent ?

14. What is a Mobile Agent ? Software program
Moves from machine to machine under its own control….
Suspend execution at any point in time, transport itself to a new machine and resume execution
Once created, a mobile agent autonomously decides which locations to visit and what instructions to perform
Continuous interaction with the agent’s originating source is not required
HOW?
Implicitly specified through the agent code
Specified through a run-time modifiable itinerary

15. Mobile Agent Derives from AI and distributed systems
Agent that migrates under its own control in a heterogeneous environment
Mobility can be
Strong: move code with current execution state
Weak: move only code
Agent
Server
Client
Server

16. Evolution Mobile Agent – transfers
BOTTOMLINE: Mobile Agents are a distributed computing paradigm
End point in the incremental evolution of mobile abstractions such as mobile code, mobile objects, mobile processes.
Mobile Code – transfers code
Mobile Object – transfers code + data
Mobile Process – transfers
code + data + thread state
Mobile Agent – transfers
code + data + thread + authority of its owner

17. Inter-Agent Message Passing - Requirements
Efficiency
Low location updating overhead
Low message delivery overhead
Asynchrony
Asynchronous execution
Little constraint on the mobile agent mobility.
Adaptability
Suit different Communication and Migration Pattern

18. Inter-Agent Message Passing - Requirements
Location Transparency
Message sender does not need to know the physical location of the receiver agent, whose address changes frequently by moving from one host to another.
Reliability
The concurrent and asynchronous nature of message forwarding and agent migration may cause message loss or chasing problem.
By reliability we mean the message can reach the target agent by a bounded number of forwarding.

19. RPC Vs Mobile Agents Mobile Agents
Instead of calling a procedure, supply the procedure as well
Messages: Mobile Agent ( procedure + data + state)
“Sending” computer may have begun the procedure and the receiving computer will continue the procedure
On-going interaction, but NO on-going communication
Requests include data which are sent as arguments to the procedure
Responses include data which are sent as results
Protocol for communication : which procedures are remotely accessible, the types of arguments and results
CLIENT
SERVER
network
Mobile
Agent
Service

20. Applets, Servlets and Mobile Agents
Applet – Downloaded from server to client
Servlet – Uploaded from client to server
Mobile Agents – Detached from client, can have multiple hops

21. Advantages of the Mobile Agent Paradigm
reduce bandwidth consumption and network loads
allow dynamic deployment of application components to arbitrary network sites
encapsulate protocols
execute asynchronously and autonomously
can adapt by moving
run on heterogeneous platforms
most distributed applications fit naturally into the mobile agent model
intuitively suitable for mobile users and disconnected operations
Mobile agents combine the strengths of techniques such as RPC, java applets etc. into a single, convenient framework

22. Levels of Mobility Weak Mobility
When moving a mobile agent carries code + data state
On moving, execution has to start from the beginning

23. Levels of Mobility Strong Mobility When moving a mobile agent carries
code + data state + execution state
Execution State – local variables and threads
On moving, execution can continue from the point it stopped on the previous host

24. MAP ?
MAP
MAP
MAP

25. Design of ARP (Adaptive and Reliable Protocol)
Mobile IP solution
Extention1: Mobile IP + Synchronization
Extension2: Distributed Home Scheme
Extension3: Mailbox-Based Scheme = ARP

26. Mobile IP Solution
MAP
MAP-Home
Reg
MAP
MAP

27. Design of ARP Mobile IP solution
No Reliability Support
Extention1: Mobile IP +Synchronization
The agent home coordinates message passing and agent migration
Extension2: Distributed Home Scheme
Extension3: Mailbox-Based Scheme = ARP

28. Mobile IP + Synchronization
MAP
MAP-Home
Reg
ACK
Dereg
MAP
MAP

29. Mobile IP + Synchronization
MAP
MAP-Home
Reg
ACK
Dereg
MAP
MAP

30. Caching Mechanism
MAP-1
MAP-2
MAP-3

31. Properties of ARP Location Transparency Reliability
Home + Caching Mechanism
Reliability
Synchronization is used
Asynchronous Migration
Adaptability
Mobile IP + Synchronization
Distributed Home Scheme
Efficiency

32. IBM’s Aglet Toolkit An Applet-like programming model for mobile agents
Java (as many mobile agent toolkits are! )
Aglet = Agent + Applet
Aglet’s API facilitates mobile technology
Aglet: mobile java object that visits aglet enabled hosts in a computer network
An Aglet = Instance of a Java class extending the Aglet Class

33. IBM’s Aglet Toolkit An Aglet =Aglet state (values in variables) +
Aglet code (class implementation)
Autonomous – runs its own thread after arriving at a host
Reactive – responds to incoming messages
Weak Mobility

34. Thank you for lessening