A Case Study on Formal Verification of Self-Adaptive Behaviors in a Decentralized System

Self-adaptation is a promising approach to manage the complexity of modern software systems. A self-adaptive system is able to adapt autonomously to internal dynamics and changing conditions in the environment to achieve particular quality goals. Our particular interest is in decentralized self-adaptive systems, in which central control of adaptation is not an option. One important challenge in self-adaptive systems, in particular those with decentralized control of adaptation, is to provide guarantees about the intended runtime qualities. In this paper, we present a case study in which we use model checking to verify behavioral properties of a decentralized self-adaptive system. Concretely, we contribute with a formalized architecture model of a decentralized traffic monitoring system and prove a number of self-adaptation properties for flexibility and robustness. To model the main processes in the system we use timed automata, and for the specification of the required properties we use timed computation tree logic. We use the Uppaal tool to specify the system and verify the flexibility and robustness properties.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432

Application-Layer Connector Synthesis

International audienceThe heterogeneity characterizing the systems populating the Ubiquitous Computing environment prevents their seamless interoperability. Heterogeneous protocols may be willing to cooperate in order to reach some common goal even though they meet dynamically and do not have a priori knowledge of each other. Despite numerous e orts have been done in the literature, the automated and run-time interoperability is still an open challenge for such environment. We consider interoperability as the ability for two Networked Systems (NSs) to communicate and correctly coordinate to achieve their goal(s). In this chapter we report the main outcomes of our past and recent research on automatically achieving protocol interoperability via connector synthesis. We consider application-layer connectors by referring to two conceptually distinct notions of connector: coordinator and mediator. The former is used when the NSs to be connected are already able to communicate but they need to be speci cally coordinated in order to reach their goal(s). The latter goes a step forward representing a solution for both achieving correct coordination and enabling communication between highly heterogeneous NSs. In the past, most of the works in the literature described e orts to the automatic synthesis of coordinators while, in recent years the focus moved also to the automatic synthesis of mediators. Within the Connect project, by considering our past experience on automatic coordinator synthesis as a baseline, we propose a formal theory of mediators and a related method for automatically eliciting a way for the protocols to interoperate. The solution we propose is the automated synthesis of emerging mediating connectors (i.e., mediators for short)

Choreography Automata

Online event due to covidInternational audienceAutomata models are well-established in many areas of computer science and are supported by a wealth of theoretical results including a wide range of algorithms and techniques to specify and analyse systems. We introduce choreography automata for the choreographic modelling of communicating systems. The projection of a choreography automaton yields a system of communicating finite-state machines. We consider both the standard asynchronous semantics of communicating systems and a synchronous variant of it. For both, the projections of well-formed automata are proved to be live as well as lock-and deadlock-free

Run Time Models in Adaptive Service Infrastructure

Software in the near ubiquitous future will need to cope with vari- ability, as software systems get deployed on an increasingly large diversity of computing platforms and operates in different execution environments. Heterogeneity of the underlying communication and computing infrastruc- ture, mobility inducing changes to the execution environments and therefore changes to the availability of resources and continuously evolving requirements require software systems to be adaptable according to the context changes. Software systems should also be reliable and meet the user's requirements and needs. Moreover, due to its pervasiveness, software systems must be de- pendable. Supporting the validation of these self-adaptive systems to ensure dependability requires a complete rethinking of the software life cycle. The traditional division among static analysis and dynamic analysis is blurred by the need to validate dynamic systems adaptation. Models play a key role in the validation of dependable systems, dynamic adaptation calls for the use of such models at run time. In this paper we describe the approach we have un- dertaken in recent projects to address the challenge of assessing dependability for adaptive software systems

Synthesis of correct and distributed adaptors for component-based systems: an automatic approach.

Building a distributed system from third-party components introduces a set of problems, mainly related to compatibility and communication. Our approach to solve these problems is to build an adaptor which forces the system to exhibit only a set of safe or desired behaviors. By exploiting an abstract and partial specification of the global behavior that must be enforced, we automatically build a centralized adaptor. It mediates the interaction among components by both performing the specified behavior and, simultaneously, avoiding possible deadlocks. However in a distributed environment it is not always possible or convenient to insert a centralized adaptor. In contrast, building a distributed adaptor might increase the applicability of the approach in a real-scale context. In this paper we show how it is possible to automatically generate a distributed adaptor by exploiting an approach to the definition of distributed IDS (Intrusion Detection Systems) filters developed by us to increase security measures in component based systems. Firstly, by taking into account a high level specification of the global behavior that must be enforced, we synthesize a behavioral model of a centralized adaptor that allows the composed system to only exhibit the specified behavior and, simultaneously, avoid possible unspecified deadlocks. This model represents a lower level specification of the global behavior that is enforced by the adaptor. Secondly, by taking into account the synthesized adaptor model, we generate a set of component filters that validate the centralized adaptor behavior by simply looking at local information. In this way we address the problem of mechanically generating correct and distributed adaptors for real-scale component-based systems

Synthesis of decentralized and concurrent adaptors for correctly assembling distributed component-based systems

Building a distributed system from third-party components introduces a set of problems, mainly related to compatibility and communication. Our existing approach to solve such problems is to build a centralized adaptor which restricts the system’s behavior to exhibit only deadlock-free and desired interactions. However, in a distributed environment such an approach is not always suitable. In this paper, we show how to automatically generate a distributed adaptor for a set of black-box components. First, by taking into account a specification of the interaction behavior of each component, we synthesize a behavioral model for a centralized glue adaptor. Second, from the synthesized adaptor model and a specification of the desired behavior that must be enforced, we generate one local adaptor for each component. The local adaptors cooperatively behave as the centralized one restricted with respect to the specified desired interactions

Studying users’ perception of IoT mobile companion apps

Internet of Things (IoT) products provide over-the-net capabilities such as remote activation, monitoring, and notifications. An associated mobile app is often provided for more convenient usage of these capabilities. The perceived quality of these companion apps can impact the success of the IoT product. We investigate the perceived quality and prominent issues of smart-home IoT mobile companion apps with the aim of deriving insights to: (i) provide guidance to end users interested in adopting IoT products; (ii) inform companion app developers and IoT producers about characteristics frequently criticized by users; (iii) highlight open research directions. We employ a mixed-methods approach, analyzing both quantitative and qualitative data. We assess the perceived quality of companion apps by quantitatively analyzing the star rating and the sentiment of 1,347,799 Android and 48,498 iOS user reviews. We identify the prominent issues that afflict companion apps by performing a qualitative manual analysis of 1,000 sampled reviews. Our analysis shows that users’ judgment has not improved over the years. A variety of functional and non-functional issues persist, such as difficulties in pairing with the device, software flakiness, poor user interfaces, and presence of issues of a socio-technical impact. Our study highlights several aspects of companion apps that require improvement in order to meet user expectations and identifies future directions

Automated Integration of Service-Oriented Software Systems

International audienceIn the near future we will be surrounded by a virtually infinite number of software applications that provide services in the digital space. This situation radically changes the way software will be produced and used: (i) software is increasingly produced according to specific goals and by integrating existing software; (ii) the focus of software production will be shifted towards reuse of third-parties software, typically black-box, that is often provided without a machine readable documentation. The evidence underlying this scenario is that the price to pay for this software availability is a lack of knowledge on the software itself, notably on its interaction behaviour. A producer will operate with software artefacts that are not completely known in terms of their functional and non-functional characteristics. The general problem is therefore directed to the ability of interacting with the artefacts to the extent the goal is reached. This is not a trivial problem given the virtually infinite interaction protocols that can be defined at application level. Different software artefacts with heterogeneous interaction protocols may need to interoperate in order to reach the goal. In this paper we focus on techniques and tools for integration code synthesis, which are able to deal with partial knowledge and automatically produce correct-by-construction service-oriented systems with respect to functional goals. The research approach we propose builds around two phases: elicit and integrate. The first concerns observation theories and techniques to elicit functional behavioural models of the interaction protocol of black-box services. The second deals with compositional theories and techniques to automatically synthesize appropriate integration means to compose the services together in order to realize a service choreography that satisfies the goal