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MODELLING OF MOBILE AGENT SYSTEMS USING dynPLA APPROACH. Agn ė Paulauskaitė-Tarasevičienė Henrikas Pranevičius. Mobile agent systems – variable structure systems. Models of variable structure systems define the systems, which in time change not only their state but the structure as well.

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modelling of mobile agent systems using dynpla approach

MODELLING OF MOBILE AGENT SYSTEMS USING dynPLA APPROACH

AgnėPaulauskaitė-Tarasevičienė

HenrikasPranevičius

mobile agent systems variable structure systems
Mobile agent systems – variable structure systems

Models of variable structure systems define the systems, which in time change not only their state but the structure as well.

  • Intelligent systems,
  • Biological systems,
  • Distributed networksystems,..

The structure of system models can change by:

  • adding new components,
  • adding new couplings between system components,
  • removing existing components,
  • removing couplings,
  • moving components from one location to another.
multi agent systems mas
Multi-AgentSystems (MAS)
  • Multi-agent systems
    • Adaptation,
    • Cooperation,
    • Mobility,
    • Autonomy,..
  • Mobile agents because of their ability to migrate, are used in the wide range of applications:
    • e-mail systems intellectualization,
    • distributed computer network management,
    • m-commerce,...
formal methods
Formal methods

Variable structure systems are complex and mostly critical therefore it is beneficial to describe them using formal methods (Petri Nets, DEVS, -calculus), which enable mathematical description and verification.

Dynamic DEVS notations:

dynDEVS (A. M. Uhrmacher),

ML-DEVS (A. M. Uhrmacher),

M-DEVS (J.H. Kim, T.G. Kim).

a piece linear aggregate method
A Piece Linear Aggregate method

Piece–Linear Aggregates (PLA) (H. Pranevičius) method is used for complex systems formalization, verification and simulation.

The PLA is taken as an object defined by:

a state Z,

input signals X,

output signals Y.

transition operators H,

output operators G.

purpose of research
Purposeofresearch

Purpose – to presentthenewconceptformodellingthe mobile agentsystemsusingaggregatemethodwithincludedAbstract Data Types.

dynamic pla dynpla
Dynamic PLA - dynPLA

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A1

A2

A3

A5

A4

1) Structural changes in dynPLA model are performed by adding and removing the elements of variable sets.

  • the removal of input signal
  • the addition of input signal

2) The external aggregate(s) is excluded in the system that would be responsible for the execution of structural changes.

structural changes in dynpla
Structuralchangesin dynPLA

1. Addition of new link; 2. Removal of link

3. Addition of aggregate 4. Removal of aggregate

5. Aggregate migration form one system to another

A1

A2

A1

A2

Anew

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A2

A2

A2

A1

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A1

In dynPLA aggregate system five types of structural changes are excluded.

abstarct data types in dynpla
Abstarct Data Typesin dynPLA

Operations:

1. AddAgR

2. RemoveR

... ... ...

Abstract Data Types (ADT) are used for definition of structural change operations in dynPLA.

ADT structure –aggregate system.

ADT operations – structural changes in aggregate system.

adt operations 1
ADT Operations (1)

Aggregatesystem

  • Mobile agent creation: OperationAddAgR, which adds a new aggregate with links, is used to describe the creation of new mobile agents.
  • Mobile agent deletion: Operation RemoveAg, which eliminates the aggregate with its entire links, is used to describe MA deletion.
adt operations 2
ADT Operations (2)

Aggregatesystem

  • Mobile agent migration: To describe agent transportation, the operationTransportAgR is used, which transports the denoted aggregate from one aggregate system to another one, adding the required links in a new place.
  • Mobile agent cloning: OperationClounAg is used to describe mobile agent cloning process, which creates the aggregate copies in an aggregate system.
formal description of included adt in dynpla
Formal description of included ADT in dynPLA

Ag_SyS

AddAgR,

RemoveAg,

TransportAgR

To define ADT in dynPLA, Object-Z specification language has been used.

unambiguous definition of structural change operations,

the preconditions, which have to be met in order to properly perform the structural changes in dynPLA model,

ADT definition in object oriented manner.

addagr operation
AddAgRoperation

Ag_Sys

A1

Anew

y1

x1

included adt advantages
IncludedADT advantages

DefinedADT allow:

to avoid the descriptions of many additional actions used in fulfillment any structural change and thereby present the specification in shorthand way;

to produce an unambiguous statement for these actions needed while performing the structural changes;

to avoid specification errors, since one can manipulate only with operations that are defined in advance.

example application of mobile agent based e commerce system
Example: Application of mobile agent-based e-commerce system

Mobile agent

User, willing to find a certain product on the internet, communicates to a User Interface Agent (UIA).

UIAcreates a MA and delegates the task to it.

MA migrates across the internet to the Data Directory (D).

MA collects all the information from the providers and returns it to UIA, which, in turn, deletes the mobile agent after getting its response.

mobile agent migration patterns
Mobile agent migration patterns

Two mobile agent migration ways are analyzed in this example:

1. Itinerary – the mobile agent visits all suppliers from the list and returns to the host server after visiting the last supplier;

2. Branching – after getting the list of providers the mobile agent clones itself according to the number of providers. Every cloned agent visits the provider assigned to it and moves to the host with gathered information.

description of mobile agent based e commerce model structural changes
Description of mobile agent-based e-commerce model structural changes

Structural changes of model are described using such ADT operations:

  • AddAgR – mobile agent creation;
  • TransportAgR – mobile agentmigration;
  • ClounAg – mobile agent cloning process, when

it migrates in branching pattern;

  • RemoveAg– mobile agent deletion.
simulation in jade
Simulationin JADE

The model was implemented in JADE software platform.

JADE has an integrated mobile agent platform.

Agent migration is realized using FIPA mobile requests protocol.

JADE provides a cloning mechanism that takes snapshot copy of an existing agent.

conclusions and remarks
Conclusions and Remarks

dynPLA model with included ADT for implementation of MA creation, removal, migration and cloning operations can be used to create various MA systems such as intellectual, distributed network and other.

The usage of ADT for description of mobile agents systems allows to significantly reduce the size of formal specification, since there is no need to additionally specify the operations that alter the system model.

In addition, there is a possibility to extend the specification by introducing the new operations if needed, that greatly increase the flexibility of structure-change modeling.