Agent Overview

Topics

• Agent and its characteristics

• Architectures• Agent Management

What is agent

• The term "agent" describes a software abstraction, an idea similar to OOP terms such as methods, functions, and objects.

• The concept of an agent provides a convenient and powerful way to describe a complex software entity that is capable of acting with a certain degree of autonomy in order to accomplish tasks on behalf of its user.

• But unlike objects, which are defined in terms of methods and attributes, an agent is defined in terms of its behavior .

Attributes of Agent

• persistence (code is not executed on demand but runs continuously and decides for itself when it should perform some activity)

• autonomy (agents have capabilities of task selection, prioritization, goal-directed behaviour, decision-making without human intervention)

• social ability (agents are able to engage other components through some sort of communication and coordination, they may collaborate on a task)

• reactivity (agents perceive the context in which they operate and react to it appropriately).

What agent is not

• Objects: • Agents are more autonomous than objects. • Agents have reactive, proactive, social.

• Expert system:• Expert systems are not coupled to their

environment; • Expert systems are not designed for reactive,

proactive behavior. • Expert systems do not consider social ability

Architecture

• Brook’s Subsumption Architecture

• BDI (Belief, desire, intention) architecture

• Layered (hybrid) architectures

Brook’s Subsumption Architecture

BDI architectures

• It defines the mental attitudes of belief, desire and intention using a modal logic

• One of the most well-known BDI architectures is the Procedural Reasoning System (PRS)

PRS

Hybrid architecture

• Horizontal and vertical layering

• In horizontal layering, the layers are directly connected to the sensory input and action output.

Horizontal layered

Vertical layered

Agent management

AP

• Agent Platform (AP): This provides the physical infrastructure in which agents are deployed. The AP consists of the machines, operating systems, FIPA agent management components, the agents themselves and any additional support software

Agent

• An agent is a computational process that inhabits an AP and typically offers one or more

• computational services that can be published as a service description.An agent must have at least one owner and must support at least one notion of identity which can be described using the FIPA Agent Identifier (AID) that labels an agent so that it may be distinguished unambiguously

Directory Facilitator

• The DF is component of an AP providing yellow pages services to other agents. It maintains an accurate, complete and timely list of agents and must provide the most current information about agents in its directory on a non-discriminatory basis to all authorized agents.

• Every agent that wishes to publicize its services to other agents should find an appropriate DF and request the registration of its agent description.

• Deregistration• Modify• Search

Agent Management System

• The AMS is a mandatory component of an AP and is responsible for managing the operation of an AP, such as the creation and deletion of agents, and overseeing the migration of agents to and from the AP. Each agent must register with an AMS in order to obtain an AID which is then retained by the AMS as a directory of all agents present within the AP and their current state (e.g. active, suspended or waiting).

• The life of an agent with an AP terminates with its deregistration from the AMS. After deregistration, the AID of that agent can be removed by the directory and can be made available to other agents who should request it. Agent descriptions can also be searched for within the AMS

Message Transport Service

• The MTS is a service provided by an AP to transport FIPAACL messages between agents on any given AP and between agents on different APs. Messages are providing a transport envelope that comprises the set of parameters detailing

• (request• :sender (agent-identifier :name alice@mydomain.com)• :receiver (agent-identifier :name bob@yourdomain.com)• :ontology travel-assistant• :language FIPA-SL• :protocol fipa-request• :content• ""((action• (agent-identifier :name bob@yourdomain.com)• (book-hotel :arrival 15/10/2006• :departure 05/07/2002 ... )• ))""• )

FIPA message structure