Self-adaptation equips a computing system with a feedback loop that enables it to deal with change caused by uncertainties during operation, such as changing availability of resources and fluctuating workloads. To ensure that the system complies with the adaptation goals, recent research suggests the use of formal techniques at runtime. Yet, existing approaches have three limitations that affect their practical applicability: (i) they ignore correctness of the behavior of the feedback loop, (ii) they rely on exhaustive verification at runtime to select adaptation options to realize the adaptation goals, which is time- and resource-demanding, and (iii) they provide limited or no support for changing adaptation goals at runtime. To tackle these shortcomings, we present ActivFORMS (Active FORmal Models for Self-adaptation). ActivFORMS contributes an end-to-end approach for engineering self-adaptive systems, spanning four main stages of the life cycle of a feedback loop: design, deployment, runtime adaptation, and evolution. We also present ActivFORMS-ta, a tool-supported instance of ActivFORMS that leverages timed automata models and statistical model checking at runtime. We validate the research results using an IoT application for building security monitoring that is deployed in Leuven. The experimental results demonstrate that ActivFORMS supports correctness of the behavior of the feedback loop, achieves the adaptation goals in an efficient way, and supports changing adaptation goals at runtime.

Self-adaptation is an established approach to deal with uncertainties that are difficult to predict before a system is deployed. A self-adaptative system employs a feedback loop that tracks changes and adapts the system accordingly to ensure its quality goals. However, making effective adaptation decisions at runtime is challenging. In this chapter we tackle two problems of effective decision making in self-adaptive systems. First, current research typically focusses on the benefits adaptaton can bring but ignores the cost of adaptation, which may invalidate the expected benefits. To tackle this problem, we introduce CB@R (Cost-Benefit analysis @ Runtime), a novel model-based approach for runtime decision-making in self-adaptive systems that handles both the benefits and costs of adaptation as first-class citizens in decision making. Second, we look into the adaptation space of self-adaptive systems, i.e. the set of adaption options to select from. For systems with a large number of adaptation options, analyzing the entire adaptation space is often not feasible given the time and resources constraints at hand. To tackle this problem, we present a machine learning approach that integrates learning with the feedback loop to select a subset of the adaption options that are valid in the current situation. We evaluate CB@R and the learning approach for a real world deployed Internet of Things (IoT) application.

Architecture-based adaptation equips a software-intensive system with a feedback loop that enables the system to adapt itself at runtime to changes to maintain its required quality goals. To guarantee the required goals, existing adaptation approaches apply exhaustive verification techniques at runtime. However these approaches are restricted to small-scale settings, which often limits their applicability in practice. To tackle this problem, we introduce an innovative architecture-based adaptation approach to solve a concrete practical problem of VersaSense: automating the management of Internet-of-Things (IoT). The approach, called MARTAS, equips a software system with a feedback loop that employs Models At Run Time and Statistical techniques to reason about the system and adapt it to ensure the required goals. We apply MARTAS to a building security case system, which is a representative IoT system deployed by VersaSense. The application comprises a set of IoT devices that communicate sensor data over a time synchronized smart mess network to a central monitoring facility. We demonstrate how MARTAS outperforms a conservative approach that is typically applied in practice and a state-of-the-art adaptation approach for different quality goals, and we report lessons learned from this industrial case. © Springer Nature Switzerland AG 2018.

Ensuring the qualities of modern software systems, such as the Internet of Things, is challenging due to various uncertainties, such as dynamics in availability of resources or changes in the environment. Self-adaptation is an established approach to deal with such uncertainties. Self-adaptation equips a software system with a feedback loop that tracks changes and adapts the system accordingly to ensure its quality goals. Current research in this area has primarily focussed on the benefits that self-adaptation can offer. However, realising adaption can also incur costs. Ignoring these costs may invalidate the expected benefits. We start with demonstrating that the costs for adaptation can be significant. To that end, we apply a state-of-the-art approach for self-adaptation to an Internet of Things (IoT) application. We then present CB@R (Cost-Benefit analysis @ Runtime), a novel model-based approach for runtime decision-making in self-adaptive systems. CB@R is inspired by the Cost-Benefit Analysis Method (CBAM), which is an established approach for analysing costs and benefits of architectural decisions. We evaluate CB@R for a real world deployed IoT application and compare it with the conservative approach applied in practice and a state-of-the-art self-adaptation approach.

Building on concepts drawn from control theory, self-adaptive software handles environmental and internal uncertainties by dynamically adjusting its architecture and parameters in response to events such as workload changes and component failures. Self-adaptive software is increasingly expected to meet strict functional and non-functional requirements in applications from areas as diverse as manufacturing, healthcare and finance. To address this need, we introduce a methodology for the systematic ENgineering of TRUstworthy Self-adaptive sofTware (ENTRUST). ENTRUST uses a combination of (1) design-time and runtime modelling and verification, and (2) industry-adopted assurance processes to develop trustworthy self-adaptive software and assurance cases arguing the suitability of the software for its intended application. To evaluate the effectiveness of our methodology, we present a tool-supported instance of ENTRUST and its use to develop proof-of-concept self-adaptive software for embedded and service-based systems from the oceanic monitoring and e-finance domains, respectively. The experimental results show that ENTRUST can be used to engineer self-adaptive software systems in different application domains and to generate dynamic assurance cases for these systems.

With the recent advances of manufacturing technologies, referred to as Industry 4.0, maintenance approaches have to be developed to fulfill the new de-mands. The technological complexity associated to Industry 4.0 makes designing maintenance solutions particularly challenging. This paper proposes a novel maintenance framework leveraging principles from self-adaptation and software architecture. The framework was tested in an operational scenario where a bearing condition in an electrical motor needs to be managed, the results showed a proper operation. As a conclusion, the proposed framework could be used to develop maintenance systems for Industry 4.0.

Modern software systems are increasingly characterized by uncertainties in the operating context and user requirements. These uncertainties are difficult to predict at design time. Achieving the quality goals of such systems depends on the ability of the software to deal with these uncertainties at runtime. A self-adaptive system employs a feedback loop to continuously monitor and adapt itself to achieve particular quality goals (i.e., adaptation goals) regardless of uncertainties. Current research applies formal techniques to provide guarantees for adaptation goals, typically using exhaustive verification techniques. Although these techniques offer strong guarantees for the goals, they suffer from well-known state explosion problem. In this thesis, we take a broader perspective and focus on two types of guarantees: (1) functional correctness of the feedback loop, and (2) guaranteeing the adaptation goals in an efficient manner. To that end, we present ActivFORMS (Active FORmal Models for Self-adaptation), a formally founded model-driven approach for engineering self-adaptive systems with guarantees. ActivFORMS achieves functional correctness by direct execution of formally verified models of the feedback loop using a reusable virtual machine. To efficiently provide guarantees for the adaptation goals with a required level of confidence, ActivFORMS applies statistical model checking at runtime. ActivFORMS supports on the fly changes of adaptation goals and updates of the verified feedback loop models that meet the changed goals. To demonstrate the applicability and effectiveness of the approach, we applied ActivFORMS in several domains: warehouse transportation, oceanic surveillance, tele assistance, and IoT building security monitoring.

Modern software systems are exposed to various types of uncertainties, such as dynamics in the available resources that are difficult to predict and goals that may change during operation. Self-adaptation equips a software system with a feedback loop that collects additional knowledge at runtime, monitors the system and adapts it when necessary to maintain its quality goals, regardless of uncertainties. One challenging problem of self-adaptation is to provide guarantees for the goals that are subject of adaptation. In this paper, we present the ActivFORMS runtime environment to realise self- adaptation with guarantees. With ActivFORMS designers model and verify a feedback loop. The verified models can directly be deployed on top of a virtual machine that executes the models to realise adaption. The approach avoids coding of the models, which is an error-prone task. The runtime environment visualises the executing models, the state of the goals, and it supports on the fly updates of the models and goals. We illustrate the approach with an adaptation scenario of an IoT building security example.

Internet of Things (IoT) consists of networked tiny embedded computers (motes) that are capable of monitoring and controlling the physical world. Examples range from building security monitoring to smart factories. A central problem of IoT is minimising the energy consumption of the motes, while guaranteeing high packet delivery performance, regardless of uncertainties such as sudden changes in traffic load and communication interference. Traditionally, to deal with uncertainties the network settings are either hand-tuned or over-provisioned, resulting in continuous network maintenance or inefficiencies. Enhancing the IoT network with self-adaptation can automate these tasks. This paper presents DeltaIoT, an exemplar that enables researchers to evaluate and compare new methods, techniques and tools for self-adaptation in IoT. DeltaIoT is the first exemplar for research on self-adaptation that provides both a simulator for offline experimentation and a physical setup that can be accessed remotely for real-world experimentation. © 2017 IEEE.