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
1. A user accesses the system and places
service requests specifying some
PSA
SWSR
criteria.
WSP
MA gets a list
of Web services
MA executes the WS
2. Creation of a MA that migrates to the
registry to find the WS that best meets
USR
the user requirements.
Transport medium
3. Service registry allows for a capability
search to be performed, since it is
MA creation
enriched with semantic information.
MA executes the WS
WSP 4. The MA, after acquiring the WS listing
MA brings the service results
Client System
and technical details, migrates to
service provider (s), invokes the WS
and collects the results
MA executes the WS
5. MA delivers the results to the user.
PSA
USR
• The MA route may vary, depending on
WSP
the user’s preferences and the
USR :User Service Requestor
MA :Mobile Agent
network topology.
RSA :Registry Stationary Agent
• WS parallel or serial execution by MA
SWSR :Semantic Web Services Registry
• WS execution locally or remotely
RSA
Users
Laptop
WSP : Web Service Provider
PSA : Provider Stationary Agent
Published services
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
Specification
Service
Policy Repository
Mobile Agent
Monitoring
Service
Event
Service
Communication Service
Trigger
Service

Communication Service

Monitoring Service filters

Event Service handles events

Trigger Service updates the

Specification service is
Policy Management Component
enables the MA to interact
with other network entities.
incoming system messages.
concerning policy changes.
policy repository when a policy
change occurs.
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 OWLS 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
N
TSTMA  RIT 

i 1
( MSPTi  ITSPi )
N
TSTWSBM  RIT   ITSPi
i 1
RIT : Registry Interaction Time
MSPTi: Migration to the ith Service Provider Time
ITSPi : Interaction Time with the ith Service Provider
Performance Evaluation test bed
Migration Time
1600
Migration time (msec)
1400
1200
1000
2
800
3
600
1
2
3
Poly. (WITH PSA)
Poly. (NO PSA)
Poly. (HYBRID)
1
400
200
0
1
10
100
1000
Service results size (KB)

“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
14000
Interaction time (msec)
12000
10000
1
2
8000
6
6000
Poly. (WITH PSA)
Poly. (NO PSA)
3
Poly. (HYBRID)
4
Poly. (WSBM)
5
Poly. (WITH PSA (CL))
6
Poly. (NO PSA (CL))
7
Poly. (HYBRID (CL))
7
4000
2
5
3
2000
1
4
0
1
10
100
Service results size (KB)
1000

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)
35
Total Service Time (sec)
30
2
25
3
20
1
Poly. (WITH PSA)
2
Poly. (NO PSA)
3
Poly. (HYBRID)
1
15
6
7
10
4
Poly. (WSBM)
5
Poly. (WITH PSA+CL)
6
Poly. (NO PSA+CL)
7
Poly. (HYBRID+CL)
5
5
4
0
1
10
100
1000
Service results size (KB)


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.
2.
3.
4.
5.
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