Safe stopping of running component-based distributed systems

Continuous availability of services and low degree of disruption are two inherent necessities for mission-critical software systems. These systems could not be stopped to perform updates because disruption in their services consequent irretrievable losses. Additionally, compared to offline update, the changes should preserve the correct completion of ongoing activities. In order to place the affected elements in a safe state before dynamic changes take place, the notion of tranquility has been proposed to make quiescence criterion less disruptive and easier to obtain. Additionally, some other approaches have been proposed in order to tackle the shortcomings of these seminal proposals. However, these approaches impose some challenges to the safe dynamic reconfiguration of component-based systems. In this paper, existing challenges to preserve global consistency during runtime software reconfiguration in distributed contexts are described. The contribution of this paper is to propose a number of guidelines which can be served as agenda for future direction of research to enable a dependable safe stopping of running component-based systems

A framework for classifying and comparing architecture-centric software evolution research

Context: Software systems are increasingly required to operate in an open world, characterized by continuous changes in the environment and in the prescribed requirements. Architecture-centric software evolution (ACSE) is considered as an approach to support software adaptation at a controllable level of abstraction in order to survive in the uncertain environment. This requires evolution in system structure and behavior that can be modeled, analyzed and evolved in a formal fashion. Existing research and practices comprise a wide spectrum of evolution-centric approaches in terms of formalisms, methods, processes and frameworks to tackle ACSE as well as empirical studies to consolidate existing research. However, there is no unified framework providing systematic insight into classification and comparison of state-of-the-art in ACSE research. Objective: We present a taxonomic scheme for a classification and comparison of existing ACSE research approaches, leading to a reflection on areas of future research. Method: We performed a systematic literature review (SLR), resulting in 4138 papers searched and 60 peer-reviewed papers considered for data collection. We populated the taxonomic scheme based on a quantitative and qualitative extraction of data items from the included studies. Results: We identified five main classification categories: (i) type of evolution, (ii) type of specification, (iii) type of architectural reasoning, (iv) runtime issues, and (v) tool support. The selected studies are compared based on their claims and supporting evidences through the scheme. Conclusion: The classification scheme provides a critical view of different aspects to be considered when addressing specific ACSE problems. Besides, the consolidation of the ACSE evidences reflects current trends and the needs for future research directions

An architectural approach to ensure globally consistent dynamic reconfiguration of component-based systems

One of the key issues that should be considered when addressing reliable evolution is to place a software system in a consistent status before and after change. This issue becomes more critical at runtime because it may lead to the failure on running missioncritical systems. In order to place the affected elements in a safe state before dynamic changes take place, the notion of tranquility has been proposed to make quiescence criterion less disruptive and easier to obtain. However, it only ensures consistency in applications with restrictive black-box design. In this paper, an architecture-based approach is proposed to preserve global consistency during runtime reconfiguration of component-based systems in distributed contexts. An initial evaluation through a prototypical implementation shows that this approach not only enables tranquility to be applicable for distributed transactions, but also significantly reduces required time to achieve a safe state and increases system availability during runtime evolution

Artifact: On the Impact of the Medium in the Effectiveness of 3D Software Visualizations

<p>The package contains the software artifacts used for evaluation in the paper "On the Impact of the Medium in the Effectiveness of 3D Software Visualizations" accepted for publication in VISSOFT 2017. </p

Low temperature structural stability of Fe₉₀Sc₁₀ nanoglasses

<p>The structural stability of Fe₉₀Sc₁₀ nanoglasses has been studied by means of low temperature crystallization. Specimens were annealed <i>in situ</i> in a transmission electron microscope, and <i>ex situ</i> in an ultra-high vacuum tube-furnace. Both studies led to similar results. The structure of the Fe₉₀Sc₁₀ nanoglasses was stable for up to 2 h when annealed at 150°C. Annealing the Fe₉₀Sc₁₀ nanoglasses at higher temperature resulted in the formation of the nanocrystalline bcc-Fe(Sc).</p> <p><b>Impact statement</b></p> <p>The structural evolution of Fe₉₀Sc₁₀ nanoglasses has been studied in detail during low temperature annealing. Our results indicate that the nanostructure of Fe₉₀Sc₁₀ nanoglasses is quite stable at low temperature.</p