Agent Framework

1
Agent Framework

• Keith Hau Dang

2
AgentOS

• Provides an environment for the development and
  the deployment of agent-based client-server
  application based on agents
• Agent
• object
• contains computational logic and state info.
• Mobile
• can migrate between hosts

3
Why AgentOS

• Break down a complex problem in to simple ones
• Take advantages of distributed computing
• Reduce communication among objects on different
  nodes
• migration

4
Overview

• AgentOS
• Agent Framework
• client
• Agent and supporting execution environment (Agent
  Context)
• AgentOS Kernel
• server
• one on each computer
• Manages agents and provides system services to
  agents

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AgentOS Kernel
Incoming Messages
Migrating Agents
II.
Router
Agent Listener
Agent Context
Multicast Group Manager
Agent
V.
Kernel
I.
Debug Agent
Inter-Agent Communication Event Pool
III.
Registry
Directory Service
Kernel Configuration
IV.
Active Agent List
Registered Home Agents
History List
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Agent Framework Components

• Agent Package used in the migration of the
  agent
• Serialized Agent (if used)
• Agent Module
• Agent Data
• Agent Context provides agents the access to the
  services and EventPool
• Service API
• Service Providers
• Event API

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Agent Framework
Agent
Agent Data
Agent Module
Serialized Agent
Agent Package
Service Providers
Service API
Event API
Agent Context
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Mobile Agents
Agent
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Agents

• autonomous mobile object
• contains computational logic
• contains state information
• Behaviors
• migration
• replication
• etc.

10
Agent Class

• public abstract class Agent implements Runnable,
  Serializable, IAgent
• protected transient IAgentContext context
• private InetAddress lastNode
• public Agent()
• public void run()
• public void onCreation(Object init)
• public void onDisposal()
• public void onDispatch() throws AgentException
• public void onArrival()
• public void onClone()
• public void onCloning() throws AgentException
• public void onActivation()
• public void migrateTo(AgentOSNode node)
• public void onDeactivation() throws
  AgentException
• public final void setAgentContext(IAgentContext
  aContext) throws

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Agent API

• public void migrateTo(AgentOSNode node)
• serialize Agent
• send Agent Module and Agent Package to new
  AgentOSNode
• public void run()
• like the main() of a C program
• execution code of the Agent
• Must always be override or agent does nothing and
  dies

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AgentOSInstance

• Unique identification of an Agent
• Contains AgentOSID
• Host information of where the Agent was created

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AgentOSInstance

• public class AgentOSInstance implements
  Serializable
• protected AgentOSID m_idStatic
• //The location in the AgentOS Network
• protected AgentOSNode m_nodeLocation
• //The creation instance
• protected long m_nInstance

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Agent Package

• Contains the Agent itself and the Agents Data
• Contains serialized agent (if used)
• Agent properties and data are stored in the Agent
  Data
• Identified by unique AgentOSID

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Agent Package Class

• public class AgentPackage implements Serializable
  
• private byte agent
• private AgentOSID m_idPkg
• private Hashtable properties
• public AgentPackage(String anAgentName, AgentOSID
  aPackageIdentifier)
• public void addProperty(AgentData aProperty)
  throws AgentPackageException
• public Object getProperty(String aPropertyName)
• public Object removeProperty(String
  aPropertyName) throws AgentPackageException

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Agent Package

• public void addProperty(AgentData aProperty)
  throws AgentPackageException
• Adds State information about Agent
• AgentData is a name/value pair
• public Object getProperty(String aPropertyName)
• Retrieves a property give the string name
• Returns an Object containing the value
• Agent must validate data type

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Agent Package cont.

• AgentOSID
• 438AA0803316BFC8BE6CCB7C0201

JVM unique number
Sequential Counter
Time Stamp
Host IP Address
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Agent Package cont.

• Agent Data
• Used to store data needed for maintaining state
• Data consists of name-value pairs
• Values can be any standard or user defined class
  instance
• The class must be contained within the Agent
  Module

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Agent Package cont.

• AgentData Class
• public class AgentData implements Serializable
• protected int determineVariant(Object obj)
• public AgentData(String aName, Object theData)

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Agent Module

• Contains Agents class files or the location of
  the class files
• Class files are stored in an AgentFileSuitcase
  object
• Two access methods local and remote
• local method access to only the class files that
  are contained with the Agent Module
• remote access retrieve the class from the
  specified location

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Agent Module cont.

• Currently only local retrieval is supported
• Security issues such as class file integrity will
  have to be worked out before remote retrieval
  methods are supported
• Prevent third parties from changing behaviors of
  the agent

22
Agent Module cont.

• Agent Module Class
• public final class AgentModule implements
  Serializable
• private Hashtable index
• private Hashtable class_files
• public synchronized byte getClassBytes(String
  s) throws ClassNotFoundException
• public synchronized Class getAgentClass(String s)
  throws ClassNotFoundException
• public synchronized void addClassFileLocator(Class
  FileLocator anIndex) throws AgentModuleException
• public synchronized void addClassFile(ClassFileLoc
  ator anIndex, byte aClassFile ) throws
  AgentModuleException

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Agent Module cont.

• public synchronized void addClassFile(ClassFileLoc
  ator anIndex, byte aClassFile ) throws
  AgentModuleException
• Add a Class File to the Module
• public synchronized Class getAgentClass(String s)
  throws ClassNotFoundException
• retrieves a Class from agent package give its name

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Agent Module cont.

• Class AgentFileSuitcase
• container for class files
• associate a string name with a class file

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Agent Module cont.

• Class AgentFileSuitcase
• public class AgentFileSuitcase implements
  Serializable
• //Stores bytes of class, or class itself
• private byte file
• private Class theClass
• private String file_name
• public AgentFileSuitcase(String aFileName, byte
  aFile)
• public AgentFileSuitcase(String aFileName, Class
  aFile)
• public AgentFileSuitcase(String aFileName, URL
  url)
• public AgentFileSuitcase(String aFileName, String
  file)

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Agent Context

• Agent execution environment
• Responsible for handing Agent requests for
  services
• Two interfaces IAgentContext and
  ISystemAgentContext
• IAgentContext is the interface for application
  agents
• ISystemAgentContext is reserved for system agents
  only

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AgentContext

• public class AgentContext extends Thread
  implements IAgentContext, IAgentContextSys
• private IAgent agent
• private AgentModule agent_module
• private AgentPackage agent_package
• private AgentClassLoader agent_loader
• private Thread agent_thread
• private long agent_sleep_time
• private long agent_run_time
• private Kernel kernel

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AgentContext

• protected void initNewAgent() throws
  AgentContextException
• public void run()
• public synchronized IServiceProvider
  getService(String aServiceName)
• public void execSerialization()
• public void execDispatch(InetAddress toLocation)
• public void execDeactivation()
• public void execTimedDeactivation(long aTime)
• public EventPool getEventPool()

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AgentContext

• public AgentContext (Kernel k, InputStream
  anInputStream) throws AgentContextException
• public AgentContext(Kernel k, URL agentURL)
  throws AgentContextException
• public AgentOSNode getNodeLocation()
• public void setAgentSleepTime(long aTime)
• public void setAgentRunTime(long aTime)
• public AgentOSInstance getAgentInstanceId()
• public AgentOSID getAgentPackageId()

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AgentClassLoader

• Loads Agent classes from Agent Module
• The class loader does not allow class from the
  'agentos. and java. namespace to be loaded
  from the Agent Module.

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AgentClassLoader

• public final class AgentClassLoader extends
  ClassLoader
• private AgentModule class_repository
• protected synchronized Class loadClass(String
  name, boolean resolve) throws ClassNotFoundExcepti
  on

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AgentInputStream

• Stream used to read in Agent Serialized Files.
• inputStream to Agent Module and Agent Package
  when an Agent migrates
• Agent Module get read first, then Agent Package