Dynamic Software Architectures
A Style-Based Modeling and Refinement Technique
with Graph Transformations
DISSERTATION
in Computer Science
submitted to the
Faculty of Computer Science,
Electrical Engineering, and Mathematics
University of Paderborn
by Sebastian Th¨
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in partial fulfillment of the requirements for the degree of
doctor rerum naturalium
(Dr. rer. nat.)
Paderborn, October 2005
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Abstract
A good architectural design allows to capture the overall complexity of large,
distributed systems at a higher level of abstraction. This is especially im-
portant for reconfigurable systems where the architectural configuration is
subject to (constant) changes at runtime. When designing such a dynamic
architecture, the software architect has to bring the functional business re-
quirements and the available communication and reconfiguration mechanisms
of the intended target platform in line.
As it is a complex task to incorporate these often diverging requirements
into the architectural model, we propose a stepwise approach similar to the
MDA initiative. We start with a platform-independent model capturing the
business requirements and add platform-specific details in a later step. For
each level of platform abstraction and associated platform, we define an ar-
chitectural style which describes the characteristics of the platform. This way,
conformance to the architectural style entails consistency between model and
the underlying platform.
Besides run-time configurations of components and connections, archi-
tectural models also comprise the description of processes that control the
communication and reconfiguration behavior. To provide operational seman-
tics, we formalize architectural models as graphs and architectural styles as
graph transformation systems. UML is added as high-level modeling language
on top, and profiles are used to adapt UML to certain architectural styles.
Due to the stepwise procedure, we also have to ensure the mutual con-
sistency between models at different levels of abstraction. For this purpose,
we define formal refinement criteria which require that both structural and
behavioral properties are preserved at the lower level of abstraction. Based
on refinement relationships between abstract and platform-specific architec-
tural styles, an algorithm allows to verify that all abstract, business-level
behavior can also be realized in the platform-specific architecture and that
no new behavior is added. These innovative refinement techniques for graph
transformation models facilitate a stepwise, platform-consistent development
of dynamic software architectures.
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To Andrea and our son Dominik.
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