web service composition. the light tower web service represents a type of signal tower device used...
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APPLICATION IN INDUSTRIAL ENVIRONMENT
Web Service Composition
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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
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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.
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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.
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EXAMPLE – TWO CONVEYORS [PUTTONEN ET AL. 2008]
Load from Left Unload to Right
Busy Failure
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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
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CONCURRENT CONVEYER OPERATION
Load from Left Unload to Right
Problem:
Conveyers may run longer than needed
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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
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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
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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
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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
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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})....
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POSSIBILITIES – MODELLING & COMPOSITION
Structured Text
Web service for
PLC
s s
s
Manual Composition via BPEL
#
IEC 61499
Web service for
PLC
s s
s
Automatic and Verified Composition
#
ExistingApproach
OurApproach
1
2