Download What is an Agent?

AGENT FRAMEWORK
ByArpan Biswas
Rahul Gupta
Agents Overview
What is an Agent?
 An agent is an entity with attributes considered useful in
a particular domain.
 In simple words, an agent is a piece of software that has
a capacity to autonomously conduct its work.
 It can also be defined as conceptual entities that
perceive and act in a proactive or reactive manner within
an environment where other agents exist and interact
with each other based on shared knowledge of
communication and representation.
Agent Overview (continued…)
 It is loosely coupled network of problem solving entities
that work together to find answer to problems that are
beyond the individual capabilities or knowledge of each
entity.
 Multiple autonomous components showing
characteristics like:
 No agent can solve problem independently
 There is no global system control
 Data is decentralized
 Computation is Asynchronous
Types of Agents
With respect to a Domain, agents can be classified as:
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Intelligent Agents
Personal Assistant Agents
Mobile Agents
Information agents
Property agent
Action agent
How does the system work?
 To interact in an open environment (like
that of Internet), agents need to overcome
two basic problems:
 Finding agents
 Agent Interaction
Finding Agents
Notion of Middle Agents.
Middle Agents
 Entities to which other agents advertise their
capabilities.
 Neither requesters nor providers from the
standpoint of transaction under consideration.
 Types of Middle Agents.
Agent Interaction
Elements to achieve Multi-Agent
Interaction:
 Communication Language and Protocol
 Format for content of communication
 Shared Ontology
Agent Communication Language
Two approaches to design ACL
 Procedural – communication is based on
executable content. E.g. Java
 Declarative- communication is based on
declarative statements like definitions,
assumptions etc. e.g. KQML
ACL (cont’d…)
Due to limitations of procedural approach,
we prefer to use declarative languages.
Declarative Language implementation
makes use of a predefined set of
messages which are structured and
classified. These are referred to as
Performatives.
ACL (Cont’d…)
Two approaches for using Performatives
 Use complex and specialized performatives.
e.g. FIPA and KQML
 Use simple performatives to perform complex
tasks. e.g. Agent-0
Performatives execute tasks like querying,
notifying, requesting, subscribing,
advertising etc.
ACL (cont’d…)
Complex performatives are advantageous
because they are efficient and avoid use
of an additional layer for interpretation of
customized messages.
On the contrary, the second approach
enables generic programming.
ACL (cont’d…)
Ontology - Agents need to use a agreed
vocabulary with a shared understanding of
the problem domain and the environment
that they can use in their communication.
Can be defined by CORBA IDL or an XML
schema or in ontology expressive
language like DAML + OIL.
ACL (cont’d…)
 Agents must discriminate between messages
according to internal state and context of
message.
 Context of a message contains information like
information about sender, receiver, message
identifier etc. which is used to differentiate the
message and act accordingly in a peer to peer
session of n-agents.
 This communication context is defined by notion
of an Envelope.
Abstract Communication Model
Nexus-a generic mode of communication.
Provides startpoint - endpoint pairs for
remote objects and a form of method
activation to start computation on remote
objects.
What is a startpoint?
What is an endpoint?
How communication occurs between
them?
ACM (Cont’d…)
Virtual Link.
Point-to-Point Communication
Special case Point-to-Point : Multicast
mode of communication
Communication of two Agents
over SOAP
HTTP SERVER
SOAP Servlet
Deployment.xml
Demux
lookup
SOAP Registry
Id
url
Id -->
SOAP Startpoint for B
METHOD: Inform
Agent A
METHOD: Inform
Agent B
Agents versus Objects
Degree of Autonomy.
Flexibility
Thread of Control
Agents and Web Services
Similarities
Use of WSDL.
Use of UDDI Registry.
XML based messaging over SOAP.
Agents and Web Services
Differences
Awareness of other peers.
Use of Ontologies.
Pro-active and Reactive.
Autonomy.
Co-operation.
Technical Challenges
Security.
Mobility.
Communication and Interoperability.
Contracts.
References
 Technologies for the Development of Agent-based Distributed
Application, Tobias Butte, ACM Crossroads.
 Agents for the Grid: A comparison with Web Services (Part 1:
Transport Layer), Luc Moreau, IEEE Conference.
 Agents for the Grid: A comparison with Web Services (Part II:
Service Discovery), Arturo Avila-Rosas, Luc Moreau, Vijay Dialani,
Simon Miles, Xiaojian Liu, IEEE Conference.
 Towards a Standardization of Multi-Agent System Frameworks,
Roberto A. Flores-Mendez, ACM Crossroads.
 Web Services and Mobile Intelligent Agents, John Fou.
 Agents as Web Services, Michael N. Hunhs, IEEE Internet
Computing, July-August 2002.
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