Mobile Agents and Ontologies

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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

USR

:User Service Requestor

MA

:Mobile Agent

RSA

:Registry Stationary Agent


SWSR

:Semantic Web Services Registry

WSP

: Web Service Provider

PSA

: Provider Stationary Agent

Service scenario

1.
A user accesses the system and places
service requests specifying some
criteria.

2.
Creation of a MA that migrates to the
registry to find the WS that best meets
the user requirements.

3.
Service registry allows for a capability
search to be performed, since it is
enriched with semantic information.

4.
The MA, after acquiring the WS listing
and technical details, migrates to
service provider (s), invokes the WS
and collects the results

5.

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




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.


Mobile Agent (MA)

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 S
WS



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

MSPT
i
: Migration to the i
th

Service Provider Time

ITSPi

: Interaction Time with the i
th

Service Provider

Performance Evaluation test bed

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 Time

between 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 :

1.
Users invoke a set of services with only one interaction with the fixed network

2.
User off
-
line operation,

3.
Better resource utilization

4.
MA dynamic behaviour improves system robustness and fault tolerance,

5.
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