Nuno Oliveira

Citation:

Oliveira N.  2015.  Architectural Reconfiguration of Interacting Services.

Thesis Type:

Abstract:

The exponential growth of information technology users and the rising of their expectations imposed a paradigmatic change in the way software systems are developed. From monolithic to modular, from centralised to distributed, from static to dynamic. Software systems are nowadays regarded as coordinated compositions of several computational blocks, distributed by different execution nodes, within flexible and dynamic architectures.
They are not flawless, though. Moreover, execution nodes may fail, new requirements may become necessary, or the deployment environment may evolve in such a way that measures of quality of service of the system become degraded. Reconfiguring, repairing, adapting, preferably in a dynamic way, became, thus, relevant issues for the software architect.
But, developing such systems right is still a challenge. In particular, current (formal) methods for characterising and analysing contextual changes and reconfiguration strategies fall behind the engineering needs.
This thesis formalises a framework, referred to as aris, for modelling and analysing architectural reconfigurations. The focus is set on the coordination layer, understood in the context of the Reo model, as it plays the key role in defining the behaviour of compositional systems. Therefore, it proposes a notion of a Coordination Pattern, as a graph-based model of the coordination layer; and of Reconfiguration Patterns, as parametric operations inducing topological changes in coordination patterns.
Properties of reconfigurations can be stated and evaluated from two different perspectives: behavioural and structural. The former compares the behavioural semantics of the reconfigured system based on whatever semantic model one associates to coordination patterns.
The latter focuses on the graph topology of the coordination pattern. Properties are expressed in a propositional hybrid logic, referring to the actual connectivity expressed in that graph.
To bring quality of service into the picture, the thesis also contributes with a new semantic model for stochastic Reo, based on interactive Markov chains. This opens new possibilities for analysis of both coordination patterns and reconfigurations. In particular for inspecting the effects of reconfigurations in the system’s quality of service, or determining reconfiguration triggers, based on the variations of the latter.
Another contribution of the thesis is the integration of aris in a monitoring strategy that enables self-adaptation and attempts to deliver it as a service in a cloud environment.
Tools are delivered to support aris. In particular, language-based technology to encode, transform and analyse coordination and reconfiguration patterns, materialises it in a dedicated editor.
All the above mentioned contributions are assessed through a case study where a static
system is worked out to support self-adaptation.

Notes:

Website: http://alfa.di.uminho.pt/~nunooliveira/downloads/thesis_phd.pdf

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