Section: Overall Objectives

Highlights of the Year

We highlight two results that are of particular interest with respect to our annual activity. Both of them deal with the reconfiguration of software systems and are related to PhD theses that have defended in 2012. The first one is concerned with the application of the notion of reconfiguration to software processes in service-oriented architectures. The second one deals with the formalization of quality of service contracts in reconfigurable software systems.

Gabriel Hermosillo’s PhD thesis [11] , that was defended on 5 June 2012, deals with reconfigurable middleware, and has provided a solution for dynamically reconfiguring business processes in service-oriented architectures. So far, our results in terms of reconfiguration were mainly in terms of fine-grained artefacts, such as components. This thesis has demonstrated that this property can be achieved for coarse-grained artefacts, such as business processes. This opens interesting perspectives, especially in terms of industrial impact, since many complex workflow activities in IT systems are expressed as business processes with stringent needs for adaptation to evolving execution conditions. Furthermore, the thesis demonstrated that the domains of Complex Event Processing (CEP)  [107] can be integrated in a comprehensive framework where events and their processing rules are the triggering conditions for process adaptation. This has resulted in the development of the Ceviche framework that was the topic of several major publications  [104] , [103] , [114] in addition to the thesis manuscript itself.

Gabriel Tamura’s PhD thesis [12] , that was defended on 28 May 2012, deals with the reliable preservation of quality of service (QoS) contracts in component-based software systems under changing conditions of execution. In response to this challenge, the presented contribution is twofold. The first one is a model for component-based software applications, QoS contracts and reconfiguration rules as typed attributed graphs, and the definition of QoS-contracts semantics as state machines in which transitions are performed as software reconfigurations. Thus, we effectively use (formal) models at runtime to reliably reconfigure software applications for preserving its QoS contracts. More specifically, we show the feasibility of exploiting design patterns at runtime in reconfiguration loops to fulfill expected QoS levels associated to specific context conditions. We realize this formal model through a component-based architecture and a reference implementation that can be used to preserve the QoS contracts of executed middleware applications. The second contribution is the characterization of adaptation properties to evaluate self-adaptive software systems in a standardized and comparable way. By its own nature, the adaptation mechanisms of self-adaptive software systems are essentially feedback loops as by defined in control theory. Thus, it is reasonable to evaluate them using the standard properties used to evaluate feedback loops, re-interpreting these properties for the software domain. We define the reliability of our formal model realization in terms of a subset of the characterized adaptation properties, and we show that these properties are guaranteed in this realization. This has resulted in the development of the QoS-CARE framework that was the topic of several major publications [66] , [67] , [63] , [127] in addition to the thesis itself.