20011130 pout a kid is slides

8/4/2019 20011130 Pout a Kid Is Slides

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Debugging Multi-agent Systems

Using Design Artifacts:

The Case of Interaction

Protocols

By David Poutakidis


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Introduction

Agents are software

Developing agents is developing software

Need appropriate design methodologiesand tools (Prometheus)

Debugging and Testing are an important

part of any system development.


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Debugging is important.

Up to 50% of the total cost/time ofdevelopment

Much of this time is spent trying to:

Locate bugs

Determine the cause of a problem

Debugging problem exacerbated by theflexibility and complexity of agent systems


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Current Debugging

Techniques

Information gathering and visualisation

Filtering applied

Color Coded messages displayed at runtime

Limitations

Too much information to digest

No process for choosing the info to display

Relies on programmer interpreting messageflow properly


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Our Approach: Make use of

Design Documents

During design, documents are produced:

which represent the developers description of

the system that describe how the system should operate

that guide the programmers during coding

Design Artifacts: interaction protocols, interaction diagrams,

scenario diagrams, capability diagrams, plandescriptors, etc


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Central Thesis:

is that the designdocumentsandsystem

modelsdevelopedwhen followinganagentbasedsoftware engineeringmethodologycanbevaluable resourcesduringthe debuggingprocessandshouldfacilitate the automaticor

semi-automaticdetectionoferrors.


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Interaction Protocols

Capture interaction patterns betweenagents

Allow choices and describe all allowableinteractions

Existing protocols developed, eg FIPA

(based on AUML)


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Buy bookBuy book

Delivery info.Delivery info.

Delivery choiceDelivery choice

Card detailsCard details

Card details requestCard details requestCard detailsCard details

ApprovalApprovalThanksThanks OrderOrder

User Shop ass. Warehouse Cashier

Credit check requestCredit check request

Details requestDetails request

Use case:

1. Customer

orders book

2. Customerspecifies delivery

3. Shop ass.

Obtains &

checks creditdetails

4. Shop ass.

thanks customer

and places order

Use Case and Interaction

Diagram


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Merchant Bank

x

Credit check request (CCR)

Card details request (CDR)

Card details (CCD)

Approve

Reject-2

Fraud

Reject-1

M1

M2

M3

M4

M5

M6

B1

B2


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Debugging with Interaction

Protocols

Agent AgentMessages

Debugger

User


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AUML not suitable for

debugger

AUML not used internally by the debugger

AUML is not precisely defined, no formal

semantics decouple the underlying representation to

allow for future versions of AUML or othernotations altogether.

We use equivalent Petri Nets internally

Clear formal semantics, algorithms and toolsfor checking properties (liveness, deadlock)


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Petri Nets Explained

Consists of Places (depicted as

circles) and Transitions

depicted as squares.

Places and Transitions linked

by arrows.

Places can contain tokenswhich indicate its marking and

the state the net is in.

Before Firing

After Firing


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Converting AUML protocol to a

Petri net equivalent.

a aP Q

P

a

QQ

P

a


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Translating AUML Connectors

a

b

AUML:

Selection

Petri net:

Selection

P

P

Q

Q

a b

R

R


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M1

CCR

B1

CDR

M2

CCD

B2

Fraud

M6

M3

M5M4

B2B2

Reject-2

Reject-1

Approve

Bank

x

Credit check request (CCR)

Card details request (CDR)

Card details (CCD)

Approve

Reject-2

Fraud

Reject-1

M1

M2

M3

M4

M5

M6

B1

B2

Merchant


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Reject-2

Reject-1

Approve

M1

CCRB1

CDR

M2

CCD

M6

B2

M3

B2B2

M4 M5

Execution of the Debugging Agent

Repeat:

1. Receive message m

2. Check m against existing protocol instances

3. Fire the Petri Net(s)

4. Examine the Petri Net(s) for erroneous

conditions.


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR

Consider the following

sequence of messages:

Merchant to bank: CCR

New protocol instance created

and token placed on M1

Token placed on CCR

Fire net

B1


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR




New protocol instance created

and token placed on M1

Token placed on CCR

Fire net

B1


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR




New protocol instance created and

token placed on M1

Token placed on CCR

Fire net

Bank to Merchant: CDR

Token placed on CDR

Fire net

B2


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





token placed on M1

Token placed on CCR

Fire net


Token placed on CDR

Fire net

Merchant to Bank:CCDToken placed on CCD

Fire Net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





token placed on M1

Token placed on CCR

Fire net


Token placed on CDR

Fire net


Fire Net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





token placed on M1

Token placed on CCR

Fire net


Token placed on CDR

Fire net


Fire Net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





Token placed on CDR

Fire net

Merchant to Bank:CCD

Token placed on CCD

Fire Net

Bank to Merchant: Approve

Token placed on approve

Fire net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





Token placed on CDR

Fire net


Token placed on CCD

Fire Net



Fire net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR





Token placed on CDR

Fire net


Token placed on CCD

Fire Net



Fire net


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR






Token placed on CCD

Fire Net



Fire net

Bank to Merchant: Fraud

Token placed on Fraud

Fire Net

Fraud


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR






Token placed on CCD

Fire Net



Fire net

Bank to Merchant: Fraud

Token placed on Fraud

Fire Net

Fraud


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Reject-2

Reject-1

Approve

M1

CDR

M2

CCD

M6

B2

B2B2

M4 M5

M3

CCR

Error encountered!!!

No transition enabled (because there is

no token on B2)

The debugging agent reports a bug: the

fraud message was unexpected

Fraud


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Future Work

Currently implementing the debuggingagent

Provide tool support to automaticallyconvert AUML protocols to Perti nets

Investigate how other design artifacts

can be used for debugging