Aida Causevic

Modeling and reasoning about service behaviors and their compositions

Service-oriented systems have recently emerged as context-independent component-based systems. Unlike components, services can be created, invoked, composed, and destroyed at run-time. Consequently, all services need a way of advertising their capabilities to the entities that will use them, and service-oriented modeling should cater for various kinds of service composition. In this paper, we show how services can be formally described by the resource-aware timed behavioral language REMES, which we extend with service-specific information, such as type, capacity, time-to-serve, etc., as well as boolean constraints on inputs, and output guarantees. Assuming a Hoare-triple model of service correctness, we show how to check it by using the strongest postcondition semantics. To provide means for connecting REMES services, we propose a hierarchical language for service composition, which allows for verifying the latters correctness. The approach is applied on an abstracted version of an intelligent shuttle system.

An Overview on the Internet of Things for Health Monitoring Systems

The aging population and the increasing healthcare cost in hospitals are spurring the advent of remote health monitoring systems. Advances in physiological sensing devices and the emergence of reliable low-power wireless network technologies have enabled the design of remote health monitoring systems. The next generation Internet, commonly referred to as Internet of Things (IoT), depicts a world populated by devices that are able to sense, process and react via the Internet. Thus, we envision health monitoring systems that support Internet connection and use this connectivity to enable better and more reliable services. This paper presents an overview on existing health monitoring systems, considering the IoT vision. We focus on recent trends and the development of health monitoring systems in terms of: (1) health parameters and frameworks, (2) wireless communication, and (3) security issues. We also identify the main limitations, requirements and advantages within these systems.

Distributed Energy Management Case Study: A Formal Approach to Analyzing Utility Functions

The service-oriented paradigm has been established to enable quicker development of new applications from already existing services. Service negotiation is a key technique to provide a way of deciding and choosing the most suitable service, out of possibly many services delivering similar functionality but having different response times, resource usages, prices, etc. In this paper, we present a formal approach to the clients-providers negotiation of distributed energy management. The models are described in our recently introduced Remes Hdcl language, with timed automata semantics that allows us to apply Uppaal-based tools for model-checking various scenarios of service negotiation. Our target is to compute ways of reaching the price- and reliability-optimal values of the utility function, at the end of the service negotiation.

Towards a Unified Behavioral Model for Component-Based and Service-Oriented Systems

There is no clear distinction between service-oriented systems (SOS) and component-based systems (CBS). However, there are several characteristics that could let one consider SOS as a step further from CBS. In this paper, we discuss the general features of CBS and SOS, while accounting for behavioral modeling in the language called REMES. First, we present REMES in the context of CBS modeling, and then we show how it can become suitable for SOS. We also discuss the relation between our model and the current state of the art.

Checking correctness of services modeled as priced timed automata

Service-Oriented Systems (SOS) have gained importance in different application domains thanks to their ability to enable reusable functionality provided via well-defined interfaces, and the increased opportunities to compose existing units, called services, into various configurations. Developing applications in such a setup, by reusing existing services, brings some concerns regarding the assurance of the expected Quality-of-Service (QoS), and correctness of the employed services. In this paper, we describe a formal mechanism of computing service guarantees, automatically. We assume service models annotated with pre- and postconditions, with their semantics given as Priced Timed Automata (PTA), and the forward analysis method for checking the service correctness w.r.t. given requirements. Under these assumptions, we show how to compute the strongest postcondition of the corresponding automata algorithmically, with respect to the specified precondition. The approach is illustrated on a small example of a service modeled as Priced Timed Automaton (PTAn).

Applying REMES behavioral modeling to PLC systems

Programmable logic controllers (PLCs), as a specialized type of embedded systems, have been introduced to increase system flexibility and reliability, but at the same time to give faster response time and lower cost of implementation. In the beginning, their use brought a revolutionary change, but with the constant growth of system complexity, it became harder to guarantee both functional and extra functional properties, as early as possible in the development process. In this paper, we show how formal methods can be applied to describe PLC-based systems and illustrate it on an example of a car wash system. First, we show how the existing behavioral modeling language REMES (resource model for embedded systems) can be extended to model the behavior of such systems. Second, we show how Remes can be translated into networks of timed automata and priced timed automata in order to support safety and resource-wise reasoning about PLC systems. The formal verification of PLC systems is carried out in the Uppaal and Uppaal Cora tools.

Analyzing Resource-Usage Impact on Component-Based Systems Performance and Reliability

An early prediction of resource utilization and its impact on system performance and reliability can reduce the overall system cost, by allowing early correction of detected problems, or changes in development plans with minimized overhead. Nowadays, researchers are using both academic and commercial models to predict such attributes, by measuring them at earliest stages of system development. In this paper, we give a short overview of existing prediction models for performance and reliability, targeting popular component-based frameworks. Next, we describe our own approach for tackling such predictions, through an illustration on a small example that deals with estimations of energy consumption.

Incorporating Attacks Modeling into Safety Process.

Systems of systems (SoS) are built as a collection of systems capable of fulfilling their own function, as well as contributing to other functionalities. They are expected to increase production efficiency and possibly decrease human involvement in harmful environments, and in many cases such systems are safety-critical. For SoS it is a paramount to provide both safety and security assurance. It is not sufficient to analyze and provide assurance of these properties independently due to their mutual connection. Hence, a joint effort addressing safety and security that provides joint guarantees on both properties, is required. In this paper we provide a safety and security assurance argument by incorporating an adversary point of view, and identify potential failures coming from the security domain that might lead to an already identified set of hazards. In this way system assets, vulnerabilities and ways to exploit them can be assessed. As an outcome mitigation strategies coming from security considerations can be captured by the safety requirements. The approach is illustrated on an autonomous quarry.