mobile agents 101

8/12/2019 Mobile Agents 101

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Agents &Mobile Agents

IntroductionAgents & Mobile Agents Shonali Krishnaswamy 1


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Would you bet 11 Million Euros onMobile Agents?


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Agents - The Concept software system which acts intelligently on

your behalf convenient metaphor situated in an environment and exhibit

behaviour which can be viewed as:pro-active, autonomous, communicative,persistent, mobile, benevolent,adaptive/learning, collaborative, reactive,

deliberative, ... stronger notions of agency: mentalistic notionssuch as knowledge, beliefs, desire, intention,goals, and a logic for reasoning with them

Cutting out the hype a kind of software andan approach to software design


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Agent Definitions Mission Impossible No consensus on a single definition

New Buzzword

Everybody wants to call their softwareAgents!

Many synonyms just to add to the

confusion knowbots, softbots, personal assistants


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What the Gurus Say Wooldridge and Jennings

A computer systemsituated in someenvironment

Capable of Autonomous Action tomeet its design objectives in thisenvironment

Autonomy ability to act without directhuman intervention


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Objects and Agents An

Analogy Agents have control of whether or not to

perform any given action

Request actions rather than invoke

methods


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Agents - Current Research andIndustry theories, architectures, languages, systems agent (internal structure) and mult-agents

(collaboration, teamwork) still thriving research -> emerging industry

>20 companies including IBM, BT, HP,Microsoft, Fujitsu, AgentSoft, Verity, AOS,Extempo, ...

>40 books on software agents at Amazon

>50 research laboratories worldwide organizations coordinating international agent

research:Agent Society, AgentLink, Agents-in-

Melbourne


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Agents - Applications many due to: appeal of the agent abstraction

agent research spans disciplines:artificial intelligence, distributedcomputing, software engineering(ABSE), sociology, psychology,

economics, object-oriented systems,artificial life, game theory, ...

a sampling...


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The Internet and theWWW impetus for information agents

gathering, filtering, sharing, monitoring,recommending, comparing information

guiding Web surfers email filtering, autoresponders (e.g., Snoop,

Smartbot)

technologies: NL processing, XML/HTML,machine learning, knowledge engineering

E.g.s: Verity, Autonomy, AgentSoft, CiFi, ...


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Electronic Commerce automate CBB stages including

product advertising, product brokering,merchant brokering, negotiation, purchase and

delivery, customer services examples for brokering and negotiation:

PersonaLogic, Firefly, BargainFinder, Jango,

Kasbah, AuctionBot, Tete-a-tete, ShopBot needs: standards for unambiguous definition of

commerce-related information such as goods,services, customer and business profiles,

electronic forms


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Business ProcessManagement streamline business processes in a more flexible

and robust manner

e.g.: ADEPT [Jennings et al]

agents representing entities negotiate forservices from each other

negotiation rules

applied to BT process for installing a network

at a customers premises prototypes based on mobile agents: intra- and

inter-organizational workflows, supply-chainmanagement in virtual enterprises, project

management


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Entertainment visual manifestation of agent

properties

e.g.s (life-like interactive animatedcharacters): Creatures game [Grandand Cliff], Extempo, MicrosoftsPersona Project (3D, conversational

parrot) believable agents - illusion of life for

objects


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Manufacturing agents systems for:

controlling manufacturing robots

managing factory production processes e.g.: YAMS

each factory and factory component is

represented by an agent automates delegation of production

orders via bidding between agents


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And More... agents for telecommunications:

network modelling and QoS

management medical informatics: e.g., multi-agent

based distributed health care systems

communityware: agents representpeople in virtual communities

distributed data mining


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Important Types of Agents

Collaborative

Interface

Mobile Information / Internet

Others Reactive, Hybrid, Smart

Many Classification Schemes &Typologies exist => to come in the nextlecture


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What is a Mobile gent? Software program

Moves from machine to machine under its owncontrol. Suspend execution at any point in time,

transport itself to a new machine and resume

execution Once created, a mobile agent autonomouslydecides which locations to visit and whatinstructions to perform

Continuous interaction with the agentsoriginating source is not required

HOW? Implicitly specified through the agent code Specified through a run-time modifiable

itinerary


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Evolution BOTTOMLINE: Mobile Agents are a distributed

computing paradigm End point in the incremental evolution of mobile

abstractions such as mobile code, mobile objects,

mobile processes. Mobile Code transfers code

Mobile Object transfers code + data

Mobile Process transferscode + data + thread state

Mobile Agent transfers

code + data + thread + authority of itsowner


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RPC Vs Mobile Agents Remote Procedure Calls (RPC)

One computer calls procedures on another Messages: Requestsand Responses

Procedure is remote i.e. it is local to the

machine that performs it Client and Server agree in advance on the

protocol for communication

Continuous on-going interaction and

communication between the client and server

CLIENT SERVERnetwork


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RPC Vs Mobile Agents Mobile Agents

Instead of calling a procedure, supply theprocedure as well

Messages: Mobile Agent ( procedure + data +state)

Sending computer may have begun theprocedure and the receiving computer willcontinue the procedure

On-going interaction, but NO on-going

communication

CLIENT

SERVER

network

Mobile

AgentService


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Applets Servlets andMobile Agents Applet Downloaded from server to

client

Servlet Uploaded from client toserver

Mobile Agents Detached fromclient, can have multiple hops


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Advantages of theMobile Agent Paradigm

reduce bandwidth consumption and network loads allow dynamic deployment of application componentsto arbitrary network sites

encapsulate protocols execute asynchronously and autonomously

can adapt by moving run on heterogeneous platforms most distributed applications fit naturally into the

mobile agent model

intuitively suitable for mobile users and disconnectedoperations Mobile agents combine the strengths of techniques

such as RPC, java applets etc. into a single, convenientframework


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Mobile Agent Myths MYTH #1:Mobile agents are risky to

use.FACT #1 : No different to allowingremote access or accepting email thatcontains active entities

MYTH #2: Mobile agent paradigmneeds a killer application to survive

FACT #2: Any technology needs timeto mature. Several applications ratherthan one killer application can alsocontribute towards pushing this

technology further


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Mobile Agent Myths

MYTH #3:Wide deployment of agentenvironments is unlikely to emerge.

Because agents execute within agiven environment. It is unlikely forsuch agent environments to beavailable on a base of computersworld wide that is large enough to

make MA applications truly ubiquitous


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Mobile Agent Myths FACT #3 : No Because

JVMs and ORBs exist in each browser(most MA applications are developed in Javaand the OMGs MASIF standards rely onCORBA compliant interfaces)

Development of PUSH technology canenable uninvited agents to execute onservers that are willing to accept them

MA toolkits are typically small in size and soare easy and inexpensive to download themon servers where they do not already exist

Emerging standards are likely to lead to

interoperable agent environments


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Mobile Agent Myths MYTH #4:Most things that

mobile agents can do, static

agents can do as well FACT #4: Truebut the

performance benefitsassociated with mobile agentscan be higher


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Levels of Mobility Weak Mobility When moving a mobile agent

carries code + data state

Data State - global or instancevariable

On moving, execution has to start

from the beginning


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Levels of Mobility Strong Mobility When moving a mobile agent carries

code + data state + execution

state Data State - global or instancevariable

Execution State local variables and

threads On moving, execution can continue

from the point it stopped on theprevious host


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Mobile Agent Toolkits What a DBMS is to Data, a Mobile Agent

Toolkit is to Mobile Agents Provides the infrastructure for mobile agents:

to interact with the underlying computersystem provide a home, a place, a

context for agents to reside in andperform their tasks on a given host to move from host to host to communicate with each other, with users

and with host servers to maintain privacy and integrity (of agentsas well as hosts)

Current trend: Java based


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Java Lingua Franca forMobile Agent Toolkits BENEFITS Platform independence Secure execution Dynamic class loading Multi-threaded programming Object serialisation


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Java Lingua Franca forMobile Agent Toolkits LIMITATIONS Inadequate support for resource

control No protected references need

for a proxy object to shield

access to public methods No support for preservation andresumption of execution state


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IBMs glet Toolkit An Applet-like programming model

for mobile agents Java (as many mobile agent toolkitsare! )

Aglet = Agent + Applet Aglets API facilitates mobiletechnology

Aglet:mobile java object thatvisits aglet enabled hosts in acomputer network

An Aglet = Instance of a Java class

extending the Aglet Class


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IBMs glet Toolkit An Aglet =

Aglet state (values invariables)+

Aglet code (classimplementation) Autonomousruns its own thread

after arriving at a host Reactive responds to incoming

messages Weak Mobility


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IBMs glet Mobile gentSystem System elements: host, engine,

context, proxy, aglet Aglet Transfer Protocol e.g.

atp://hostname:port/context/

AgletID: system-given globallyunique identifier for life


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IBMs glet Mobile gentSystem

agletproxy

proxyaglet

context

aglet proxyproxy aglet

contextengine host

user


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IBMs glet System

Proxy: representative of an aglet. Shields and protects an aglet from directaccess to its public methods

Provides location transparency for the

objectContext: an aglets work place.

A server can have several contexts.

Named StationaryMessage: objects exchanged between aglets

Synchronous and Asynchronous messagingusin FUTURE REPLY


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The Aglet Model Operations on aglets:

creationwithin a context. Assign id,initialise and execute. run

cloningidentical copy in the samecontext. Different id and executionthread

dispatching move from one context

to another where execution will re-start (i.e. threads do not migrate) retractionpull from current

context and insert into the context

from which retractionwas requested


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The Aglet Model activation & deactivation

temporary halt and store insecondary storage disposal halt execution and remove

from current context

Event-based control via user-definedmethods: onCreation, onDisposing,onCloning, onDispatching, onReverting,onArrival, onActivation,

onDeactivating, Messaging between aglets: messaging via

proxy, a message invokes a method


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Several OtherToolkits Gossip - Tryllian

GrasshopperIKV++ Technologies

DAgents - Dartmouth University

Voyager - ObjectSpace

MOA - Mobile Objects and Agents - The Open

Group Research Institute Concordia - Mitsubishi Electric Lab

JSeal, Gypsy, GossipMany, many more


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Mobile Agent Applications WWW Information Retrieval Electronic Marketplace

Distributed Data Mining Mobile Computing

Space Presence

OthersNetwork Management,

Distributed Database Access


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Mobile WebRobots/Spiders Send mobile agents to the server side to

search/filter through web pages and

send only the relevant pages (or parts ofpages) back

Deploy mobile agents to index web

pagesanalyse and construct partialindexes on the server sideand send

back the index


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Mobile WebRobots/Spiders Effective use of internet bandwidth

Better performance

Filtering of data and avoiding transfer ofintermediate data

Better load distribution

Continue scanning and screening even ifthe link goes down


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Electronic Marketplace Widely quoted application domain for mobile

agents

Electronic Marketplace: Suppliers, Dealers,

Buyersand Brokers

Buyers are generally the most benefited bymobile agents

Transaction Phases

Information Phasebuyer collects information

from many prospective suppliers

Negotiation Phasebuyer and supplier negotiate

the conditions of the transaction

Execution PhaseActual exchange of goods


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Electronic Marketplace Market Structures

Direct Search Markets

Buyer directly contacts different suppliers

Buyer has to perform the entire information

phase

Time consuming and expensive

Mobile Agents are ideally suited to perform

the search


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Electronic Marketplace Brokered Markets

Brokers perform the search for a certain fee

Here brokers use mobile agents instead of the

buyers

Dealer Markets Dealers are required to buy products in advance and

offer them at set prices to buyers

Buyer asks different dealers for prices and

immediately buys the product at the cheapest dealer

Mobile agents can be used to find the cheapest price

offered


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MA Applications:Electronic Marketplace Auction Markets

Centralise supplies and demands on a single

virtual market place

Less need for mobile agents as suppliers andbuyers can see the potential trading partners


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Distributed DataMining

Data Mining (DM):Discovery of hitherto unknownpatterns from very large databases

Distributed Data Mining (DDM):Data mining ofdistributed data sources

Characteristics: Distribution of data, users, mining algorithms and

computational resources

Heterogeneity of data

Large data volumes DDM = DM + Knowledge Integration


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Distributed DataMining Client Server Model for DDM:Bring data from

distributed sources into a data mining server formining.

Disadvantage:Communication Overhead

Mobile Agent Model:Dispatch mining agents to thedistributed data sites.

Overcomes the communication bottleneck

But the problem of non-dedicated computational

resources Our Work Hybrid DDM Model


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Delivering Services toMobile Devices Environment: a set of wireless/wired networkedmobile/fixed computers dynamic environment: computational resources, battery

power, memory, bandwidth (with frequentdisconnections) limitedand varyingfor the same

computerand across computers; set of computers in adomain varying some uses of mobile software/agents:

move/off-load (multiple) computations to other sites(e.g., processing at database, Web and WAP servers):

no need to maintain connection, depleting resources,move to discovered resources software components only when and where needed:

cope with limited memory, zero-maintenance mobilecomputers, different versions for different hardware

characteristics


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Delivering Services toMobile Devices users service environment can follow usersmobile device (e.g., VHE, NetChaser) agents move to mobile devices to perform

tasks (e.g., monitor and gather information

from deployed mobile devices) research: mobile places, docking stations e.g.SOMA, AgentTcl, MASE (ACTS CLIMATE),Magenta, Tacoma, Discovery


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Current Areas of Work mobile agent theories: Pi-calculus extensions,Mobile Ambients, Agent Itineraries

mobile agent model: some component-based,AI-based

mobile agent infrastructure: environmentsupporting mobile agents - security, naming,domain crossing, etc

mobile agent programming: languages, toolkits,abstractions

mobile agent applications: mobile agentstandards: OMGs MASIF, FIPA


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Research Issues Security: protect host from agents, protect agents

from agents,protect agents from host Performance: if Java or Python, performance

penalities with interpretation (esp. for performancecritical applications), but not for long?

Strong mobility: move full execution state (stacksetc), stacks not accessible with current Java?

MA management:

how control and manage deployed agents

issues: fault tolerance (e.g., agent fails, hostfails), recalling agents, tracking agents, servicingagents (esp. longer living agents)

mobile agents 101

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