Outline

1. COCOA : Conversation-Based Service Composition for Pervasive Computing EnvironmentsSonia Ben Mokhtar, Nikolaos Georgantas and Valérie IssarnyICPS'06 : IEEE International Conference on Pervasive Services 200626-29 June 2006, Lyon, France

2. Outline • Background • COCOA : COnversation based service COmposition for pervAsive computing environments • Prototype Implementation and Evaluation • Conclusion and Future Work

3. Pervasive Computing Environments and SOA Standard Service description Standard protocol e-learning Heterogeneity Multimedia streaming e-shopping Travel reservation

4. Example Scenario

5. Pervasive Computing Environments • Mobile nodes host services providing various functionalities • Mobile users need to perform tasks anytime anywhere, using functionalities of the pervasive environment • Challenges • Allow users to perform tasks, by composing “on the fly” available networked services • Enable autonomy and adaptation to the environment’s changes

6. Issues & Requirements • Existing approaches to “ad hoc” service composition in pervasive computing environments • Commonly assume that services have been pre-developed to integrate • Poorly deal with the environment’s dynamics and heterogeneity • Requirements • Deal with the environment’s heterogeneity • Semantic Web services • Deal with the environment’s dynamics • Automating service discovery and composition User tasks realized through dynamic composition of networked services

7. Semantic Web services • Web Services • A software component developed using any language, deployed on any platform, described using WSDL, accessible via remote calls using SOAP on top of internet protocols • Web Services in pervasive computing environments (e.g. WSAmI [ISTS04]) • Semantic Web Services • Semantically annotating Web services descriptions using Ontologies • Semantic annotation on top of WSDL, e.g., WSDL-S • Web Service Ontologies, e.g., OWL-S, WSMO,FLOWS, ROWS

8. OWL-S based Model for Services and Tasks • Service • Workflow of high level provided capabilities • A set of non-functional properties • Task • Workflow of high level required capabilities (abstract capabilities) • A set of non-functional requirements • Matching • High level capabilities (Service discovery and selection) • Workflows (Service integration) Networked Services User Task Browse Browse Browse Required Capability Provided Capabilities

9. Service Discovery & Composition-COCOA ?: Service Discovery ? ? ? ? ? ? ? ? Service Composition Abstract user task conversation

10. Service Advertised capability (Adv) required inputs (Adv.In) provided outputs (Adv.Out) provided properties (Adv.P) Service Requested capability (Req) provided inputs (Req.In), required outputs (Req.Out) required properties (Req.P) COCOA-SD: Semantic Matching of Service Capabilities Client Service Ontologies

11. COCOA-CI: Modelling conversations as finite state automata • A model to map OWL-S conversations to finite state automata • A mapping rule for each OWL-S control construct (e.g. Choice, Sequence, While, Split) • Translate the problem of dynamic conversation integration to an automata analysis problem

12. COCOA-CI : Conversation Integration-Example 3 1 1 2 3 4 5 5 4 2

13. COCOA-CI: Binding to Concrete Services • Each composed capability corresponds to either an atomic or a composite process of a networked service

14. Properties of COCOA-CI • Workflow integration • Interleaving • The number of services to be composed is dynamic • The degree of involvement of each composed service is dynamic COCOA-CI Networked services 1 2 3 4 Service 2 Service 1 1 3 2 4 1 2 3 4 COCOA-CI Networked services Service 1 Service 2 COCOA-CI COCOA-CI Networked services-Env 1 Networked services-Env 2

15. COCOA in action… COCOA-SD COCOA-SD COCOA-CI

16. Prototype Implementation and Evaluation • Implementation of COCOA-CI • Runtime environment • Java, Linux platform running on an Intel Pentium 4, 2.80 GHz CPU with 512 MB of memory • Services : from 1 to 100 of semantically equivalent capabilities • Evaluation of the runtime overhead produced by integrating conversations • Comparison with the XML parsing time of services and tasks (mandatory)

17. Prototype Implementation and Evaluation • Task : composed of a single required capability • The runtime overhead of COCOA-CI is negligible compared to the XML parsing time of services and task descriptions

18. Prototype Implementation and Evaluation (2) • Task : from 1 to 20 of semantically equivalent capabilities in sequence • The runtime overhead of COCOA-CI depends on the number intermediate paths assessed during the composition • Here : for a task composed of i capabilities there are 100 ipossible composition schemes

19. Prototype Implementation and Evaluation (3) • Realistic scenario • 20 required capabilities • 30 available capabilities • Various control constructs • 32 ms for finding the 2 possible compositions among 36 intermediate compositions • 152 ms for XML parsing of service and task descriptions • In most realistic cases the runtime overhead of COCOA-CI is negligible compared to XML parsing time

20. Conclusion & Future work • COCOA : Conversation-based Service Composition in Pervasive Computing Environments • A flexible approach for dynamically composing services to perform a user task • Built upon Web services and Semantic Web paradigms • Based on conversation integration • Ongoing work • Advanced prototype implementation (including QoS- and Context-awareness) underway as a part of the European IST AMIGO project • Integration of COCOA into a semi-distributed discovery protocol adapted for pervasive computing environments [Sailhan,Percom’05] • Efficient matching of semantic Web service capabilities • Reconfiguration of the composed user task at runtime

21. Questions ? Allez Les Bleus !