APPLICATION IN INDUSTRIAL ENVIRONMENT

Web Service Composition

The light tower web service represents a type of signal tower device used in production systems.

A production device can be viewed as a web service when it is connected to an appropriately programmed controller

http://www.youtube.com/watch?v=dBtMQddY-dQ&list=UUmQ6R1Aku6ltqhcMCFhigQg&index=5&feature=plcp

http://www.sciencedirect.com/science/article/pii/S147403461000039X

INDUSTRIAL EQUIPMENTS AS WEB SERVICES

WEB SERVICES IN INDUSTRIAL ENVIRONMENT

Traditionally, industrial systems are controlled by the Programmable Logic Controllers (PLCs).

Now - Empowering the systems in production industry with SOA benefits.

The production lines can be decomposed into smaller equipment pieces.

Each piece of the equipment is abstracted through a web service.

SERVICE COMPOSITION IN INDUSTRIAL ENVIRONMENT

The composition of web services in order to fulfil customer needs allows the creation of loosely-coupled production systems,

Giving possibilities for reconfiguration as new and possibly previously unforeseen needs are introduced into the system

Other service composition advantages.

EXAMPLE – TWO CONVEYORS [PUTTONEN ET AL. 2008]

Load from Left Unload to Right

Busy Failure

SEQUENTIAL CONVEYER OPERATION

Load from Left Unload to Right

Problem:

Only one conveyor may run at a time. Thus,in practise, the pallet would stop at the end of conveyor

CONCURRENT CONVEYER OPERATION

Load from Left Unload to Right

Problem:

Conveyers may run longer than needed

PROBLEMS WITH BPEL

Does not address conformance and QoS.

Deals with connectivity only, not with correctness.

Turing-complete language, more about implementation than specification.

Cannot verify properties of a composition result

Source: Nikola MilanovicHumboldt University, Berlin

OUR SOLUTION – FORMAL VERIFICATION

Unload to right / Success

Load from Left/Success

ConveyorService

Load from Left Busy

Unload to Right

Failure

Load from Left Success

Unload to Right

Success

Load from Left/Busy

Unload to right / Failure

Unloaded Loaded

FSMS FOR LEFT AND RIGHT CONVEYORS

Unload to right / Success

Load from Left/Success

Load from Left/Busy

Unload to right / Failure

Unloaded Loaded

Unload to right / Success

Load from Left/Success

Unload to right / Failure

Unloaded LoadedLoad from Left/Busy

PRODUCT COMPOSITION

Load from Left, T

UL, UL L, UL

UL, L L, L

Unload to right, T

Unload to right ,Load from

Left

T, Unload to right

ON THE FLY COMPOSITION

Load from Left, T

UL, UL L, UL

UL, L L, L

T, Unload to right

Unload to right ,Load from

Left

CTL Specifications1- AG ({UL, UL} => AX({L, UL}))2- AG (Not {L,L})3- AG ({L,UL} U {UL, L})....

POSSIBILITIES – MODELLING & COMPOSITION

Structured Text

Web service for

PLC

s s

s

Manual Composition via BPEL

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IEC 61499

Web service for

PLC

s s

s

Automatic and Verified Composition

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ExistingApproach

OurApproach

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