Abstract: Design decisions made during early development stages of self-adaptive systems tend to have a significant impact upon system properties at runtime (e.g., safety, QoS). However, understanding the implications of these decisions a priori is difficult due to the different types and degrees of uncertainty that affect such systems (e.g., simplifying assumptions, human-in-the-loop). To provide some assurances about self-adaptive system designs, evidence can be gathered from activities such as simulations and prototyping, but these demand a significant effort and do not provide a systematic way of dealing with uncertainty. In this chapter, we describe an approach based on model checking of stochastic multiplayer games (SMGs) that enables developers to approximate the behavioral envelope of a self-adaptive system by analyzing best- and worst-case scenarios of alternative designs for self-adaptation mechanisms. Compared to other sources of evidence, such as simulations or prototypes, our approach provides developers with a preliminary understanding of adaptation behavior with less effort, and without the need to have any specific adaptation algorithms or infrastructure in place. We illustrate our approach by showing how it can be used to mitigate different types of uncertainty in contexts such as self-protecting systems, proactive latency-aware adaptation, and human-in-the-loop.

Abstract: Software systems are increasingly called upon to autonomously manage their goals in changing contexts and environments, and under evolving requirements. In some circumstances, autonomous systems cannot be fully automated but instead cooperate with human operators to maintain and adapt themselves. Furthermore, there are times when a choice should be made between doing a manual or automated repair. Involving operators in self-adaptation should itself be adaptive, and consider aspects such as the training, attention, and ability of operators. Not only do these aspects change from person to person, but they may change with the same person. These aspects make the choice of whether to involve humans non-obvious. Self-adaptive systems should trade-off whether to involve operators, taking these aspects into consideration along with other business qualities it is attempting to achieve. In this chapter, we identify the various roles that operators can perform in cooperating with self-adaptive systems. We focus on humans as effectors - doing tasks which are difficult or infeasible to automate. We describe how we modified our self-adaptive framework, Rainbow, to involve operators in this way, which involved choosing suitable human models and integrating them into the existing utility trade-off decision models of Rainbow. We use probabilistic modeling and quantitative verification to analyze the trade-offs of involving humans in adaptation, and complement our study with experiments to show how different business preferences and modalities of human involvement may result in different outcomes.

Abstract: Many self-adaptive systems benefit from human involvement, where a human operator can provide expertise not available to the system and perform adaptations involving physical changes that cannot be automated. However, a lack of transparency and intelligibility of system goals and the autonomous behaviors enacted to achieve them may hinder a human operator's effort to make such involvement effective. Explanation is sometimes helpful to allow the human to understand why the system is making certain decisions. However, explanations come with costs in terms of, e.g., delayed actions. Hence, it is not always obvious whether explanations will improve the satisfaction of system goals and, if so, when to provide them to the operator. In this work, we define a formal framework for reasoning about explanations of adaptive system behaviors and the conditions under which they are warranted. Specifically, we characterize explanations in terms of their impact on a human operator's ability to effectively engage in adaptive actions. We then present a decision-making approach for planning in self-adaptation that leverages a probabilistic reasoning tool to determine when the explanation should be used in an adaptation strategy in order to improve overall system utility. We illustrate our approach in a representative scenario for the application of an adaptive news website in the context of potential denial-of-service attacks.

Abstract: As Cyber-Physical Systems (CPSs) become more autonomous, it becomes harder for humans who interact with the CPSs to understand the behavior of the systems. Particularly for CPSs that must perform tasks while optimizing for multiple quality objectives and acting under uncertainty, it can be difficult for humans to understand the system behavior generated by an automated planner. This work-in-progress presents an approach at clarifying system behavior through interactive explanation by allowing end-users to ask Why and Why-Not questions about specific behaviors of the system, and providing answers in the form of contrastive explanation.

Abstract: Internet of Things (IoT) allows for cyber-physical applications to be created and composed to provide intelligent support or automation of end-user tasks. For many of such tasks, human participation is crucial to the success and the quality of the tasks. The cyber systems should proactively request help from the humans to accomplish the tasks when needed. However, the outcome of such system-human synergy may be affected by factors external to the systems. Failure to consider those factors when involving human participants in the tasks may result in suboptimal performance and negative experience on the humans. In this paper, we propose an approach for automated generation of control strategies of cyber-human systems. We investigate how explicit modeling of human participant can be used in automated planning to generate cooperative strategy of human and system to achieve a given task, by means of which best and appropriately utilize the human. Specifically, our approach consists of: (1) a formal framework for modeling cooperation between cyber system and human, and (2) a formalization of system-human cooperative task planning as strategy synthesis of stochastic multiplayer game. We illustrate our approach through an example of indoor air quality control in smart homes.

Abstract: Self-adaptive systems overcome many of the limitations of human supervision in complex software-intensive systems

by endowing them with the ability to automatically adapt their

structure and behavior in the presence of runtime changes.

However, adaptation in some classes of systems (e.g., safety- critical) can benefit by receiving information from humans (e.g.,

acting as sophisticated sensors, decision-makers), or by involving

them as system-level effectors to execute adaptations (e.g., when

automation is not possible, or as a fallback mechanism). However,

human participants are influenced by factors external to the

system (e.g., training level, fatigue) that affect the likelihood

of success when they perform a task, its duration, or even if

they are willing to perform it in the first place. Without careful

consideration of these factors, it is unclear how to decide when to

involve humans in adaptation, and in which way. In this paper,

we investigate how the explicit modeling of human participants

can provide a better insight into the trade-offs of involving

humans in adaptation. We contribute a formal framework to

reason about human involvement in self-adaptation, focusing on

the role of human participants as actors (i.e., effectors) during

the execution stage of adaptation. The approach consists of:

(i) a language to express adaptation models that capture factors

affecting human behavior and its interactions with the system,

and (ii) a formalization of these adaptation models as stochastic

multiplayer games (SMGs) that can be used to analyze human- system-environment interactions. We illustrate our approach in

an adaptive industrial middleware used to monitor and manage

sensor networks in renewable energy production plants.

Abstract: Self-Adaptive systems are expected to adapt to unanticipated run-time events using imperfect information about their environment. This entails handling the effects of uncertainties in decision-making, which are not always considered as a first-class concern. This technical report summarizes a set of existing techniques and insights into addressing uncertainty in self-adaptive systems and outlines a future research agenda on uncertainty management in self-adaptive systems. The material in this report is strongly informed by our own research in the area, and is therefore not necessarily representative of other works.