A Platform for Rapid Composition of
Web Services in a Peer-to-Peer Environment
Quan Z. Sheng, Boualem Benatallah, Eileen Oi-Yan Mak
University of New South Wales, Sydney, Australia
Marlon DumasQueensland University of Technology, Brisbane, Australia
SELF-SERV provides a platform for rapid composition of Web se-rvices, where Web services are declaratively composed, and the resulting composite services are executed in a peer-to-peer and dynamic environment.
SELF-SERV distinguishes three types of services: elementary ser-vices, composite services, and service communities. Composite services are described through statecharts. Service communit-ies perform dynamic provider selection through selection poli-cies.
Pool of servicesand containers
User Layer
Communication Layer
is registered with
Elementaryservices
Containers
Composite services
is composed of
workflow database web-accessible programs
C1 C2 C3
CS1 CS2
ES1 ES2 ES4
Directory Layer
Conversation Layer
Service Layer
Internet
SOAP messages
Service registries
Service templates
1. Overview
SELF-SERV Service Manager
2. Service CreationThe Service Builder provides a statechart editor for describing composite service operations. It also offers search and browse facilities to locate operations from existing services and import them into composite services. It provides an editor for describing service operations, loading and configuring SELF-SERV built-in classes (e.g., linking an operation to a scoring service of a commun-ity).
Domestic Flight Booking (DFB)
Intl Travel Arrangement (ITA)
Accommodation Booking (AB)
Car Rental (CR)
AttractionsSearch (AS)
[domestic(destination)]
[not domestic(destination)]
[near(major_attraction, accommodation)]
[not near(major_attraction, accommodation)]
Complete Travel Service (CTS)
Intl. FlightBooking (IFB)
Travel Insurance (TI)
Intl Travel Arrangements Service (ITAS)
AS
DFB
ITA
AB
CR
IFB TI
CTS
wrapper
coordinator
3. Service DeploymentThe deployment of a composite service requires the generation and deployment of routing tables (i.e., precondition/postprocessing tables of each state of a composite service statechart). The routing tables (XML documents) are then uploaded into the hosts of the corresponding component services, together with the wrapper and coordinator classes.
4. Service Discovery EngineServices are published in a UDDI registry and located through the Service Discovery Engine.
5. Service Execution
CTS
ASS CRS ABS ITAS
TIS
IFBS
AS CR AB ITA TI
IFBASS
CF
IC
CF CF
IC IC IC
IC
IC
CFCF
CF CF
CFCF
IC
IC
wrapper
coordinator
control-flow notificationCF
service invocation/ completion
SELF-SERV adopts an orchestration model based on peer-to-peer interactions between software components hosted by the providers participating in the composition. The or-chestration of a com-position service exe-cution involves two types of messages: control flow notifica-tions and service invo-cations/completions.
CF
6. Performance Evaluation
No. of component service
Deployment cost (second)
15 20 30 40 50
8.9 10.1 13.1 15.9 19.0
No. of component service
Deployment cost (second)
60 70 80 90 100
21.8 25.9 30.2 32.9 34.1
Deployment cost of composite services.
We conducted several experiments to study the performance of SELF-SERV using a cluster of PCs.
The results show that the deployment speed is acceptable, and that the peer-to-peer approachto composite service execution leads to increa-sed throughput through better workload distri-bution.
Workload allocation.
Execution time with different message sizes.
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