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Explore the integration of Mobile Agents and Semantically enriched Web Services for wireless users accessing services in a fixed network, utilizing an enhanced WS registry for semantic matching. Evaluate performance variants and system interactions.
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Wireless Web Services using Mobile Agents and Ontologies V. Baousis, E. Zavitsanos, V. Spiliopoulos, S. Hadjiefthymiades, L. Merakos, G. Veronis Pervasive Computing Research Group Communication Networks Laboratory Dept. of Informatics & Telecommunications, University of Athens, Greece. ICPS 2006 Lyon, France, June 26 – 29, 2006
Outline • Introduction • Platform overview • Performance evaluation • Conclusions -Future work
Introduction • We propose the integration of Mobile Agents (MA) and Semantically enriched Web Services (SWS) for wireless users who access SWS in the fixed network. • MA transport themselves from one system to another and invoke SWS while being in the same host or network with the SWS. • The system uses an enhanced WS registry that provides semantic matching to incoming service queries and the published SWS descriptions.
Platform overview • Service scenario • A user accesses the system and places service requests specifying some criteria. • Creation of a MA that migrates to the registry to find the WS that best meets the user requirements. • Service registry allows for a capability search to be performed, since it is enriched with semantic information. • The MA, after acquiring the WS listing and technical details, migrates to service provider (s), invokes the WS and collects the results • MA delivers the results to the user. • The MA route may vary, depending on the user’s preferences and the network topology. • WS parallel or serial execution by MA • WS execution locally or remotely • USR :User Service Requestor • MA :Mobile Agent • RSA :Registry Stationary Agent • SWSR :Semantic Web Services Registry • WSP : Web Service Provider • PSA : Provider Stationary Agent
Mobile Agent (MA) • User representative in the fixed network • Moves, finds, executes SWS and delivers results to the user. • May spawn clones to execute the selected WS in parallel. • Important components are: • The data state contains the information carried by the MA during migrations. • The policies specifies the autonomous behaviour of the MA (migration, cloning). • The matching engine is responsible for post-processing the service registry query results.
MA- Policy Management component • Communication Service enables the MA to interact with other network entities. • Monitoring Service filters incoming system messages. • Event Service handles events concerning policy changes. • Trigger Service updates the policy repository when a policy change occurs. • Specification service is responsible for fulfilling this task.
SW Services Registry (SWSR) • Consists of the RSA, the matchmaking tool and the UDDI registry. • The Matchmaker enhances the UDDI by adding capability-based discovery and in combination with Racer, processes the OWL ontologies. • Semantic information in SWS descriptions are passed to the OWL-S matchmaking engine. • The Matchmaker maps the OWL-S service description to UDDI.
Registry Stationary Agent (RSA) • Acts as a broker between the MA and the service registry. • Implements part of the registry’s functionality and serves MA’s requests. • MA does not have to be aware of the registry implementation details.
Provider Stationary Agent (PSA) • Resides in the host offering a SWS. • Wraps the SWS functionality and delivers service results to MA • Communicates with the SWS through SOAP. • MA communicates with PSA with RMI. • PSA existence is indicated in the WS description • MA need not be SOAP fluent • PSA methods are multi-threaded
Web Service Provider (WSP) • Provides the SWS • SWS expressed in WSDL and OWL-S. • WSDL (Service grounding) • OWL-S (Service profile and model). • SWS can expose a PSA to act as delegate and interact with the user’s MA
Performance Evaluation We have developed and evaluated the following system variants: • A WS system implemented with the “Conventional WS Business Model” (WSBM). • Our MA framework with stationary agents in Service registry and Service providers - (WITH PSA.) • Our MA framework without stationary agents in Service registry and Service providers - (NO PSA.) • A hybrid system, where some Service Providers accommodate a Stationary agent, while others do not (Hybrid.) Terms RIT : Registry Interaction Time MSPTi: Migration to the ith Service Provider Time ITSPi : Interaction Time with the ith Service Provider
Migration Time • “With PSA” system exhibits constantly less migration time from the hybrid approach and the latter exhibits constantly less from the “No PSA”. • “With PSA” system the MA agent does not have to be SOAP fluent i.e., it does not have to carry extra code in order to support such communication.
Interaction Time • Better performance sequence: WSBM, “With PSA”, “Hybrid” and “No PSA” system. The same performance sequence is observed when CL is enabled (lines 5,7,6). • Systems with PSA communicate faster than systems communicating with SOAP. • The better inter-agent communication is attributed to the Mobile Agent Platform used, where agents communicate with synchronous inter-agent message passing.
Total Service Time (TST) • Besides WSBM, the system with the lowest service time is that having PSA and MA cloning enabled. • MA cloning increases the Interaction Timebetween the MA and the WS but, eventually, entails considerable improvement to the system (due to WS parallel execution).
Conclusions-Future work • A framework for wireless access to semantically enriched WS using MA. • The main advantages of the system are : • Users invoke a set of services with only one interaction with the fixed network • User off-line operation, • Better resource utilization • MA dynamic behaviour improves system robustness and fault tolerance, • New services, agents, users and service registries can be easily integrated to the framework thus providing an expandable, open system. Future work • Study of agent mobility for efficient composition of SWS invocation (implement routing algorithms and considering network status and topology). • Integration with SNMP agents for network performance monitoring.
Thank you for your attention… Questions? http://p-comp.di.uoa.gr, http://cnl.di.uoa.gr ICPS 2006 Lyon, France, June 26 – 29, 2006