12-06-2012, 02:29 PM
MOBILE AGENTS
MOBILE AGENTS .pptx (Size: 702.3 KB / Downloads: 41)
Mobile Code Systems: Design
Four basic types:
Client/Server
Code on Demand
Remote Evaluation
Mobile Agents
Elements
Data (stored result sets)
Code (commands)
Program stack (current status of the program)
Code on Demand Discussion
The idea behind code-on-demand was the thin client or network computer (created by Larry Allison)
Examples: Java Applets
Elements
data – static
code - mobile
program stack - static
Advantages
simple software update mechanisms
Disadvantages
long delay for start up
Remote Evaluation
A prominent example is SQL (to a certain extent), postscript.
Elements
data - static
code - mobile
program stack - static
Advantages
sometimes better to move the code and not the data (search
video database, Postscript)
Disadvantages
difficult to debug
security problems
What is a Mobile Agent?
Program that can migrate from system to system within a network environment
Performs some processing at each host
Agent decides when and where to move next
How does it move ?
Save state
Transport saved state to next system
Resume execution of saved state
Events in Mobile Agent’s life-time
Retraction: an agent is brought back from a remote host along with its state to the home machine.
Disposal: an agent is terminated and its state is lost forever.
Communication: Notifies the agent to handle messages incoming from other agents , which is the primary means of inter-agent correspondence.