Aglets

1
Aglets

• Based on Mobile Agents with Java The Aglet API
  by Danny B. Lange and Mitsuru Oshima

2
Their Definition of Agent

• A software object
• Mandatory properties
• reactive
• autonomous
• goal-driven
• temporally continous

3
Seven Good Reasons (I)

• Reduce network load through mobility
• Overcome network latency
• Encapsulate protocols -- dealing with legacy
  systems
• Execute asynchronously and autonomously

4
Seven Good Reasons (II)

• Adapt dynamically
• Naturally heterogeneous
• Robust and fault-tolerant
• can find better hosts
• can distribute tasks
• work redundantly

5
Pos. Agent Chars. of Java (I)

• Platform independent
• Secure execution
• no illegal type casting
• no pointer arithmetic
• byte code is checked before execution
• Dynamic class loading
• Multithread programming
• synchronization primitives

6
Pos. Agent Chars. of Java (II)

• Object serialization
• Reflection

7
Neg. Agent Chars. of Java (I)

• No resource control
• CPU cycles
• memory
• GUI handles
• No protection of references
• access to public methods
• proxy

8
Neg. Agent Chars. of Java (II)

• No object ownership of references
• garbage collection
• memory, GUIs not released
• agent kept alive against its will (with reference
  to agent)
• No support for preservation and resumption of
  execution state
• no access to virtual machine, program counter,
  etc.

9
Basic Concepts of Aglets

• Aglet
• Proxy
• Context
• Message
• synchronous and asynchronous
• Future reply
• Identifier

10
Basic Operation on Aglets

• Create
• Clone
• Dispatch
• Retract
• Activate and deactivate
• Dispose
• Send and receive messages