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this level, we have distributed members exchanging messages, with service provi-
sion involving several members and messages. The behaviours could be specified
following an action-based paradigm, making abstractions of the state changes
of individual members, and focusing on the sequence of messages that are ex-
changed and how they are concurrently processed. In addition, behavioral prop-
erties express the results of exchanging series of messages. Thus, we may consider
specification languages based on process algebras, particularly CSP [10] and CCS
[14]. However, both CSP and CCS assume a fixed set of communication channels,
which is incompatible with our approach. While pi-calculus [15] supports dynam-
ically created channels, it is less convenient to express multicasting behaviours
which are the cornerstone of our approach.
The main contribution of this work is the definition of a formal model con-
stituting a foundation (or more precisely its fragment) for specifying messaging
services. This foundation specifies a set of operations that can be later used as
primitive operators for defining messaging services at different levels of abstrac-
tion. In particular, we specified a refinement of the abstract model based on
communication channels, and defined an extensibility mechanism to build high-
level communication services. We also demonstrated how this mechanism can
address some requirements of the Electronic Government domain.
8
Conclusions
We presented the ongoing development of foundations to enable programmable
messaging for Electronic Government. The motivation, existing solutions and
their limitations were presented in Section 1, followed by a brief introduction to
Electronic Government in Section 2. Section 3 introduced an example business
process implementing cross-agency delivery of licensing services. The foundation
for programmable messaging was presented in Section 4, from abstract state and
state-changing operations, through messages, to concrete operations to register
and unregister members, create and destroy channels, subscribe and unsubscribe
to channels, and send and receive messages. The case study in Section 3 was
revisitedinSection5toexplainhowthemessaging services introduced in Section
4 can support communication needs of the licensing process. Section 6 presented
the design of prototype software implementing the concepts of programmable
messaging. Related work was discussed in Section 7.
Future work includes completing the definition of the model for core messaging
services, including the definition of iteration, specifying and implementing hor-
izontal and vertical extensions based on core services, and verifying behavioral
properties of such extensions and their compositions.
Acknowledgments. We wish to thank Adegboyega Ojo, Gabriel Oteniya and
Pablo Fillottrani for collaboration and comments about this work. This work was
partly supported by Macao S.A.R. Government under the e-Macao Program.
 
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