Doctoral theses authored or mentored by Vincenzo De Florio

• Vincenzo De Florio (2000-10-13). A Fault-Tolerance Linguistic Structure for Distributed Applications. Doctoral dissertation, Dept. of Electrical Engineering, University of Leuven, Belgium. 212 pages. ISBN 90-5682-266-7.
  Abstract: The structures for the expression of fault-tolerance provisions into the application software are the central topic of this dissertation. Structuring techniques provide means to control complexity, the latter being a relevant factor for the introduction of design faults. This fact and the ever increasing complexity of today's distributed software justify the need for simple, coherent, and effective structures for the expression of fault-tolerance in the application software. A first contribution of this dissertation is the definition of a base of structural attributes with which application-level fault-tolerance structures can be qualitatively assessed and compared with each other and with respect to the above mentioned need. This result is then used to provide an elaborated survey of the state-of-the-art of software fault-tolerance structures. The key contribution of this work is a novel structuring technique for the expression of the fault-tolerance design concerns in the application layer of those distributed software systems that are characterised by soft real-time requirements and with a number of processing nodes known at compile-time. The main thesis of this dissertation is that this new structuring technique is capable of exhibiting satisfactory values of the structural attributes in the domain of soft real-time, distributed and parallel applications. Following this novel approach, beside the conventional programming language addressing the functional design concerns, a special-purpose linguistic structure (the so-called recovery language) is available to address error recovery and reconfiguration. This recovery language comes into play as soon as an error is detected by an underlying error detection layer, or when some erroneous condition is signalled by the application processes. Error recovery and reconfiguration are specified as a set of guarded actions, i.e., actions that require a pre-condition to be fulfilled in order to be executed. Recovery actions deal with coarse-grained entities of the application and pre-conditions query the current state of those entities. An important added value of this so-called recovery language approach is that the executable code is structured so that the portion addressing fault-tolerance is distinct and separated from the rest of the code. This allows for division of complexity into distinct blocks that can be tackled independently of each other. This dissertation also describes a prototype of a compliant architecture that has been developed in the framework of two ESPRIT projects. The approach is illustrated via a few case studies. Some preliminary steps towards an overall analysis and assessment of the novel approach are contributed by means of reliability models, discrete mathematics, and simulations. Finally, it is described how the recovery language approach may serve as a harness with which to trade optimally the complexity of failure mode against number and type of faults being tolerated. This would provide dynamic adaptation of the application to the variations in the fault model of the environment.

• Hong Sun (2011-10-04). Adaptive Service Orchestration in Ambient Assisted Living. Doctoral dissertation, Dept. of Mathematics and Computer Science, University of Antwerp, Belgium. 116 pages. Front page
  Abstract:We are now living in a world where we are continuously interacting with various service systems in our daily lives, ranging from ordering a pizza online to filing a tax form. Businesses, hospitals, education systems, cities and even a nation could be considered as instances of service system. Service innovation is earnestly required to improve the current service systems by combining innovations in technology, business models, social organizations and users' demand. This thesis discusses service innovation in the domain of Ambient Assisted Living. The population of elderly people is increasing rapidly in the last decades, which becomes a predominant aspect of our societies. As such, both efficacious and cost-effective solutions need to be sought to provide services required by an ever increasing number of users. The European Union launched the Ambient Assisted Living Joint Programme in 2008, which aims to find out an efficient solution to help elderly people living independently. Many research projects are supported by the AAL programme; meanwhile, many similar projects are also carried out in the rest of the world. Living assistance systems and assistive devices are thus developed to facilitate the daily lives of the elderly people. These technologies show promise in helping elderly people to live independently and in comfort. However, most of the research on AAL is focused on assisting the elderly people with technologies, such as assistive devices. In order to utilize all the resources and build up efficient and cost effective systems to help the elderly people independently living, it is important to take a deeper perspective of such systems with the view of service system. This thesis proposes to build up a mutual assistance community where services from informal care-givers (e.g. families, friends, etc.) are also included in addition to those from assistive devices. Besides passively receiving services as service requesters, the mutual assistance community also provides user with the possibility to join group activities as peer participants. Such group activities may contribute to greatly save the social resources, at the same time also helping the elderly people live in an active way. A simplified mutual assistance community simulation model was built up for simulAting community behaviours of such a system. An adaptive framework was built by combining Service Oriented Architecture (SOA) and Aspect Oriented Programming (AOP). This framework could be used to monitor environment changes and orchestrate service adaptations in the mutual assistance community. Semantic service matching is investigated, and applying semantic service matching in the mutual assistance community is also carried out in this thesis. The scope of this thesis is to prove the feasibility of the mutual assisted community concept by means of a few contributions and simulations. Constructing and validating such a community is a huge task, which is not implemented in this thesis due to resource limitation.

• Ning Gui (2012-09-17). Middleware-based adaptation evolution with reusable adaptation components. Doctoral dissertation, Dept. of Mathematics and Computer Science, University of Antwerp, Belgium. 196 pages.
  Abstract: With recent development of mobile and pervasive computing, software applications are increasingly expected to dynamically adjust their behaviours according to the highly dynamic environments they are deployed in Applications must sense the environment changes and reacting upon those changes based on their contextual knowledge. For each new context, a new adaptation logic is required. This results in the high complexity of adaptive software development, especially for changing environments. Multiple approaches have been proposed to facilitate the development of adaptive systems. However, such works mostly focused on providing support for particular set of systems and with pre-defined quality-of-service optimization goals. Therefore, they are costly to reuse in new systems and hard to adjust to other concerns. How to streamline the engineering of adaptation with multiple and evolving combinations of concerns remains a largely unexplored topic. This work addresses this issue from two aspects: Firstly, a novel adaptive framework is proposed by extending the separation of concerns paradigm to adaptation logics design. System's global adaptation behaviour is contextually constructed with multiple reusable adaptation modules each of which embeds an adaptation strategy limited to one or more concerns. Rather than assuming these strategies to be orthogonal and thus not interfering with each other, this framework provides a systematic and customizable conflict detection policy and resolution mechanism. Secondly, a modular middleware architecture is designed to facilitate the incremental deployment of new and unforeseen adaptation modules. Software engineers are provided with the ability to add/remove/update adaptation modules during run-time. Development of adaptation modules is simplified by factoring out common adaptation mechanisms. Our approach, embodied in an adaptation framework called Transformer, provides an engineering approach to monitor a target system and its environment, detect opportunities for improvements, select a course of adaptation strategies, resolve possible conflicts and apply changes to a software architecture. Our work was compared to the state of the art from both theoretical and practical viewpoints. Design evaluation and experiment results show that our system has significant advantage over traditional approaches in light of flexibility and reusability of the adaptation modules, with little complexity and performance overhead. Moreover, our framework was applied in a practical case study---autonomous robots control. Experience gained from this case justified that both the framework design and modular middleware-based implementation add significant value to developers in designing and incorporating new adaptation logics.