communicating transaction processes

21.10.02 ES Seminar 1

Communicating Transaction Processes

P.S. ThiagarajanNational University of Singapore

Joint Work with: Abhik Roychoudhury; ……


The Main Features

• To support System Level Design– One Level of Abstraction higher than C, C++,

VHDL ..• UML-compatible

– MSCS + Asynchronous control flow– Based on MSCs (Message Sequence Charts)– Sequence Diagrams


Why System Level Design?

• Closer to end-use(r) .• Less detailed and more architecture-neutral.• Easier reuse/adaptaton.• Easier to verify.

– Safety-critical applications need to be correct.– Catch design errors early.– Coupling with a correct-by-construction

synthesis method is an attractive option.


What is Available?

• Data flow graphs.• Automata of various kinds.• Petri nets.• State charts.• Esterel, Lustre.• SDL, UML.


Why UML-compatible?

• UML is getting rapidly established as a standard.– Mainly in software engineering projects– Increasingly so in embedded systems domain.

• Offers a suite of graphical notations:– Multiple views– Behavioral and structural diagrams.– Object orientation.

Reuse, adaptation


An Idealized Design FlowRequirements

Exec. Specifications.

Intermediate representation

SW/HW Implementation.

High Level Description


Requirements and Exec. Specifications

• Requirements : Message Sequence Charts (MSCs)

• Exec. Specifications :– State charts.

• UML supports both but no clear distinction made.• Other Exec. Spec. :

– Petri nets, – MPAs (Message Passing Automata), ….


MSCs

• Message Sequence Charts:– Describe scenarios.– A finite pattern of interaction between agents

(object instances,..).– A story


Message Sequence Charts

rq

U1 R

rq

yn

U2



rq

U1 R

rq

yn

U2



rq

U1 R

rq

yn

U2

internal action



rq

U1 R

rq

yn

U2

internal actions



rq

U1 R

rq

yn

U2


CTPs

• Communicating Transaction Processes.• An executable spec. mechanism.

– Based on MSCs.• A network of interacting agents.

– Agent’s interaction pattern behavior: Standard distributed system model

– Interaction: Guarded choice of MSCs. Transaction schemes.


Distributed System Models

• Petri nets• Data flow graphs• Statecharts• Distributed transition systems (many

kinds!)• Process algebras (CCS, CSP, …)


PI1 IB1 IB2 PI2

I1

B

I2

P2


PI1 IB1 IB2 PI2

I1

B

I2

P2

But the boxes will have internal structure.

A complex Transaction Scheme.


Transaction Scheme

waitcount2:= waitcount2 + 1

2data.present & B.free 2data.present & B.free

I2 B

reqy

adddata

I2 B

reqn

I2 B

2data.present


PI1 IB1 IB2 PI2

I1

B

I2

reqy

adddata

2data.present & B.free


PI1 IB1 IB2 PI2

I1

B

I2

reqy

adddata



P11

I1

1data.present

no-op

1data.present

1data.present

no-data

1data.present

1data.present

data

1data.present

P11 Transaction SchemeI1


Analysis Issues

• Determine whether a CTP is bounded.• Determine if a CTP can deadlock.• Determine if a CTP is well-formed.

Current Status

The CTP Model

SMV ES Representation

Verilog

AnalysisVerification

Simulation;

Synthesis

Case Studies

Modeling

Current Status

The CTP Model

SMV ES Representation

Verilog

AnalysisVerification

Simulation;

Synthesis

Case Studies

Modeling

Pankaj Jain

Nikhil Jain

Kamrul Hasan Talukdar

Tran Tuan Anh

Ge Zhiguo


Future Work

• Add multiple instances of a process.– Object features

• Add timing constraints.• Develop the computational model.

– Interactions with environment (sense, actuate)– Computational steps (control law)– Schedulability is a key issue.

• HW/SW Partitioning; Architectural mapping; Synthesis?

communicating transaction processes

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