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An agent is implemented as an instance of a CLOS class. agent class and script-agent class are defined by AgenTalk. An application program should define a class based on one of these classes.

Agent Class

Class: agent

agent class provides the basic functionalities of an agent (such as creating a new process for this agent, sending and receiving messages).

Class: script-agent

script-agent class provides additional functionalities of an agent which use the script facility. If an agent uses a script, script-agent class must be an ancestor of the agent's class. Note that script-agent is a subclass of agent.

Agent Name

An agent has a unique name. A message can be sent by specifying the name of a receiver agent; it is not necessary to specify where the agent is.

The name of an agent is given in the form of local-name@location-name. Each location has a post-office, which handles message delivery. In other words, each post-office has a unique location-name. By registering an agent at the post-office, an agent can receive messages from other agents.

In the Common Lisp implmentation, each Lisp system has one post-offcie, and has a location-name. The location-name in an agent name can be omitted, if agents are in the same location (in the same Lisp system).

Note: The agent name is case-insensitive.

Agent-related Functions

An agent is created using the make-instance generic function. The name of an agent should be specified by :name initarg option. Thus, :name initarg option cannot be used by your application. When a symbol is given as an agent name, its symbol-name is used.

Generic Function: add-agent agent &optional process-run-function &rest args

Primary Method: add-agent (agent agent) &optional process-run-function &rest args

This function registers agent at a post-office. In addition, a new process (thread) is created in a Lisp system for agent. At this time, process-run-function is invoked with arguments given by args. The default value of process-run-function is the generic function agent-toplevel.

Generic Function: agent-toplevel agent &rest args

Primary Method: agent-toplevel (agent agent) &rest ignored

Primary Method: agent-toplevel (agent script-agent) script-name &rest args

The generic function agent-toplevel provides a default toplevel loop for an agent. The method for agent repeatedly retrieves a message from a queue associated with agent, and searches for a message handler and invokes the message handler found.

The method for script-agent accepts script-name as an argument. The script with the name script-name is invoked when this agent is started. args specifies the arguments passed to this script invocation (see section Script).

Function: find-agent name &optional errorp

This function returns the agent whose name is given by name. name can be a string or a symbol. When a symbol is given, its symbol-name is used. If an agent whose name is name is not found, an error is signaled if errorp is non-nil, and nil is returned if errorp is nil (which is the default).

Function: agent-name agent

This function returns a name of agent as a string.

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