Building Self-adaptive Software Systems with Component, Services & Agents Technologies: Self-OSGi - Agents and Artificial Intelligence - page 310

make those available under a common umbrella. Active components are autonomous
acting entities (like agents) that can use message passing as well as method calls (like
active objects) for interaction. They may be hierarchically structured and are managed
by an infrastructure that ensures important non-functional properties (like components).
The AC framework has been realized in the Jadex AC platform. In particular, Jadex
AC runs on an extended Jade platform and supports component types (kernels) for BDI
agents, as well as simpler, task-specific agent models. Noticeably, such an approach
defines a proprietary component or agent frameworks and does not leverage mainstream
component-based initiatives and standards, such as OSGi.

8 Conclusions and Future Work

This paper has examined component, service and agent concepts, and has illustrated
the design and the implementation of the Self -OSGi framework for the construction of
systems with Self-* properties. Self -OSGi is built over OSGi technology by leveraging
previously unexploited similarities between component & service and the BDI agent
model.
Compared to similar CBSE initatives, such as the A-OSGi framework reviewed in
Section 3.2, Self -OSGi provides re-usable, lightweight, modular end extensible adap-
tation mechanisms at component-level granularity that are also tightly integrated with
the OSGi Declarative Service framework. Self -OSGi can be used to drive the selection
of services, control the on-demand instantiation of the components implementing them,
and monitor their performance to drive their future selection and to recover from fail-
ure. In contrast, A-OSGi can be used to control and monitor entire bundles, but does
not offer any mechanism to discern the performance among the single components and
services inside the bundle or to instantiate them on-demand.
In addition, the association with the BDI model allows Self -OSGi to leverage well-
defined adaptation policies and results from BDI-related research.
Compared to existing AOSE/CBSE integration approaches, such as the SoSAA and
the AC framework reviewed in Section 7, Self -OSGi provides a highly modular re-
alization of the BDI agent model, which is grounded in the mechanisms offered by
a mainstream component & service technology. This results in low performance and
footprint overheads and fast system's adaptation, as shown in Section 6. Noticeably,
existing agent platforms, such as JADE, have already been made compatible with the
OSGi framework. However, this is usually done by encapsulating the entire agent plat-
form into a single, monolithic OSGi bundle. Such an approach does not benefit of the
increased modularity enabled by the OSGi framework.
In contrast, one of the goal of the Self -OSGi framework is to evolve into a modular
and interoperable agent platform. In addition, future research work with Self -OSGi will
seek to adapt agent/planning integration and agent learning techniques to tackle some of
the main limitations of adaptive component & service frameworks (which are common
to basic procedural agent systems), such as their lack of look-ahead capabilities and
their reliance on hard-coded pre-conditions of component plans.

Acknowledgements. This work has been supported by the EU FP7 RUBICON project
(contract n. 269914).