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Presentation at the International Conference for Web Services 2011. Presented with Best Student Paper Award. Imagine using mobile device capabilities and participatory sensing to create new value-added services from existing device services
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Lero© 2011
Opportunistic composition of sequentially-connected services in mobile computing environments
Christin Groba and Siobhán Clarke – Trinity College Dublin
IEEE International Conference of Web ServicesWashington D.C., 5th July 2011
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Mobile environments are the new frontier for service providers
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Getting to the airport
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Fastest route
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Disruption
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What is the fastest alternative ?
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What is the fastest alternative ?
Walk 3 minBus in 6 min
Walk 5 min
RealityWalk 5 min
Browsing the Web
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How to obtain real-time data?
Utilise mobile device capabilities & participatory sensing
GPS Accel Navi Camera
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Real-time data as decision support
Real-time dataWalk 5 min
Real-time dataWalk 5 min
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Mobility and resource scarcity make service composition challenging
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Challenge: Dynamic setting
No central controlHigh failure probability
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Challenge: Energy scarcity
Wireless communication drains battery
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Emergence of dynamic ad hoc environments has led to decentralised composition algorithms
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Decentralised composition
Binding
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Decentralised composition
Binding
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Decentralised composition
Binding
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Decentralised composition
Binding
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Decentralised composition
Binding
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Decentralised composition
Binding
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Decentralised composition
Binding
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Decentralised composition
BindingExecution
Once all service are bound, execution can start
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Many decentralised composition approaches bind providers too early
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Bound but not used
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Disconnect Recovery Communication Energy
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How to reduce failure probability?
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Reduce the delay between service binding and service execution
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Opportunistic execution model
Binding
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Opportunistic execution model
BindingExecution
Execute service while searching for the next provider
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Opportunistic execution model
BindingExecution
Execute service while searching for the next provider
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Opportunistic execution model
BindingExecution
Execute service while searching for the next provider
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Opportunistic execution model
BindingExecution
No unnecessary binding of conditional paths
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Opportunistic execution model
BindingExecution
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Opportunistic execution model
Bind available provider
BindingExecution
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Opportunistic execution model
Provider likely to be still available if execution follows immediately after binding
BindingExecution
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Opportunistic execution model
BindingExecution
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System model
Abstract composite request
< composite > := seq(< composite >;< composite >) |< type > | < type >:< provider >
< type > := S1 |…| Sn< provider > := P1 |…| Pm
Directory-less, on demand discovery
Proximity-based selection
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Evaluation
Simulation Jist/SWANS UlmRandom Waypoint
Controlled Composition lengthNode speed
Metric Success ratioResponse timeCommunication effort
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Do composites execute to completion?
Opportunistic model 28% more successful
Node speed: 1-13 m/s80
60
40
20
0
Suc
cess
ratio
(%)
4 5 Composition length
6 7
baselineopportunistic
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Do composites respond to initiator quicker?
Opportunistic model 33% faster
Node speed: 1-13 m/s
8
6
4
2
0
Res
pons
e tim
e (s
)
4 5Composition length
6 7
baselineopportunistic
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Node speed: 1-13 m/s120
0
4 5Composition length
6 7
baselineopportunistic
100
80
60
40
20
Num
ber o
f sen
t mes
sage
s
Do composites communicate unnecessarily?
Opportunistic model 14% less chatty
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Current & Future work
Service flowsService requests contain splitting and merging paths
Failure recoveryComposition success cannot be guaranteed and recovery strategies are essential
PrivacyParticipants aware of control and data flow which may include sensitive information
Device heterogeneityResource-poor devices require light-weight integration concept
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Recap
New frontier Share mobile device capabilities and create new value-added service composites
Challenge How to reduce the failure probability of service composites?
Approach Reduce delay between binding and execution
Results More successful, faster, and less chatty than “first bind all then execute” approach
Current work Service flows and failure recovery
Future work Privacy and device heterogeneity
Thank you!
Lero© 2011
