gathering and combining the required context infor-
mation, how to secure the whole context provision-
ing process, and how is the cooperation between the
providers of context achieved, and even enforced?
Barkhuus and Dey identified three levels of in-
teractivity for context-aware applications (Barkhuus
and Dey, 2003): personalization, active context-
awareness, and passive context-awareness. For both
authors, personalization is motivated by the diver-
sity and dynamics featuring nowadays applications.
For active context-awareness, it concerns applications
that, on the basis of sensor data, change their content
autonomously. In passive context-awareness applica-
tions present the updated context to the user and let
the user specify how the application should change.
In (Baresi et al., 2005), Baresi et al. proposed a
policy-based approach to monitor Web services’ func-
tional (e.g., constraints on exchanged data) and non-
functional (e.g., security, reliability) requirements. In
this approach the authors report on the different types
of policies that can be defined along the life cycle of
a Web service (Mukhi et al., 2004). These policy
types are service policies, server policies, supported
policies, and requested policies. The combination of
requested and supported policies results in effective
policies.
5 CONCLUSION
In this paper, we presented
C P 4W S method, which
is one step towards offering the appropriate support
to those who are responsible for the design and devel-
opment of Web services-based systems. Composition
of Web services addresses the situation of a user’s re-
quest that cannot be satisfied by any single, available
Web service, whereas a composite Web service ob-
tained by combining a set of available Web services
might be used. The core concepts of
C P 4W S are
context, policy, service chart diagram, state chart di-
agram, and resource. By developing context-based,
policy-driven Web services, it would be possible to
handle the aspects of the environment in which these
Web services will operate. These aspects are multi-
ple and can be related to users (e.g., stationary, mo-
bile), time of day (e.g., in the afternoon, in the morn-
ing), etc.
ACKNOWLEDGEMENTS
C P 4W S development benefited from the discus-
sions the authors had with A. Anderson, G. Kouadri-
Most
´
efaoui, S. Sattanathan, and Ph. Thiran.
REFERENCES
Anderson, A. H. (2004). An Introduction to The Web Ser-
vices Policy Language (SWPL). In Proceedings of
The 5th IEEE International Workshop on Policies for
Distributed Systems and Networks (POLICY’2004),
New-York, USA.
Baresi, L., Guinea, S., and Plebani, P. (2005). WS-Policy
for Service Monitoring. In Proceedings of The 6th
Workshop on Technologies for E-Services (TES’2005)
held in conjunction with The 31st International Con-
ference on Very Large Data Bases (VLDB’2005),
Throndeim, Norway.
Barkhuus, L. and Dey, A. (2003). Is Context-Aware Com-
puting taking Control away from The User? Three
levels of Interactivity Examined. In Proceedings
of The Fifth International Conference on Ubiqui-
tous Computing (UbiComp’2003), Seattle, Washing-
ton, USA.
Booch, G. and Rumbaugh, J. and Jacobson, I. (1998)). The
Unified Modeling Language User Guide . Addison-
Wesley Professional.
Breener, M. and Schiffers, M. (2003). Applying Web Ser-
vices Technologies to the Management of Context
Provisioning. In Proceedings of The 10th Workshop
of the OpenView University Association (OVUA2003),
Geneva, Switzerland.
Coutaz, J., Crowley, J. L., Dobson, S., and Garlan, D.
(2005). Context is Key. Communications of the ACM,
48(3).
Keidl, M. and Kemper, A. (2004). A Framework for
Context-Aware Adaptable Web Services. In Proceed-
ings of The 9th International Conference on Extend-
ing Database Technology (EDBT’2004), Heraklion,
Crete.
Lupu, E. and Sloman, M. (1999). Conflicts in Policy-Based
Distributed Systems Management. IEEE Transactions
on Software Engineering, 25(6).
Maamar, Z., Benslimane, B., Mrissa, M., and Ghedira, C.
(2006a). C ooP S - Towards a Method for Coordi-
nating Personalized Services. Software and System
Modeling Journal Special Section on ”Service-Based
Software and Systems Engineering”, Springer Verlag,
5(2).
Maamar, Z., Benslimane, D., and Anderson, A. (2006b).
Using Policies to Manage Composite Web Services.
IEEE IT Professional, 8(5).
Maamar, Z., Kouadri Most
´
efaoui, S., and Yahyaoui, H.
(2005). Towards an Agent-based and Context-
oriented Approach for Web Services Composition.
IEEE Transactions on Knowledge and Data Engineer-
ing, 17(5).
Mukhi, N., Plebani, P., Silva-Lepe, I., and Mikalsen, T.
(2004). Supporting Policy-Driven Behaviors in Web
Services: Experiences and Issues. In Proceedings of
The 2nd International Conference on Service Oriented
Computing (ICSOC’2004), New York City, NY, USA.
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