Modeling and Formal Analysis of e-Health Systems

Abstract: With the healthcare practice being increasingly dependent on digital processes and electronic communication, there is a need to support a variety of e-Health applications of different requirements, with respect to connectivity, low latency, and high reliability. The focus of this thesis is on providing formal assurance to systems supporting e-Health applications. Among such systems, this thesis considers: a) Ambient Assisted Living (AAL) Systems, aimed to assist the elderly in their independent and safe living within their homes, and b) healthcare assistance systems that include home, hospital, or emergency e-Health applications, where simultaneous access and communication is critical.In order to provide formal assurance, one needs to  capture both the structure and behavior of the targeted e-Health systems within models that can be formalized and analyzed by formal methods. Due to only few existing initiatives in the AAL domain that integrate common AAL functionalities such as pulse monitoring, fall detection, as well as fire detection, and remote communication with care-givers, within a generic framework, in this thesis, we propose, as a first contribution, two different categories of AAL architecture frameworks onto which different functionalities, chosen based on user preferences, can be integrated. The first solution follows a centralized approach, using an intelligent Decision Support System, and the second employs a distributed architectural approach, involving multiple intelligent agents. Although centralized solutions are easy to develop, scalability, flexibility, multiple user accesses and potential self-healing are easier to achieve with the distributed, agent-based architecture.  To formally assure these solutions against functional, timing and reliability requirements, as a second contribution, we model the architectures in one of the architecture description languages, namely Architecture Analysis and Design Language, to which we assign semantics in terms of various flavors of transition systems. Consequently, we employ corresponding model checking techniques, such as exhaustive model checking in UPPAAL, statistical model checking in UPPAAL SMC, and probabilistic Model Checking in PRISM, to provide the necessary design-time assurance. Our AAL formal frameworks abstract away the communication media and assume communication protocols with fixed delays only. Moreover, their scope is limited to home-based assistance with with no simultaneous/parallel user access. Hence, we model next the communication media and expand our scope to target generic e-Health systems supporting home, hospital, and emergency use cases. For such systems, networking capabilities with real-time and reliable communication schemes are essential for service-user connectivity, and resource sharing.One communication scheme employed in such e-Health applications is the fifth generation of cellular wireless technology, namely, 5G, which offers the possibility of creating network slices that provide independent logical networks, to serve a variety of applications characterized by certain quality-of-service requirements. The network slicing is enabled by the underlying 5G service orchestration capabilities that deal with virtual network function placement, implicit resource assignment, and traffic routing.In this work, we study in detail the service orchestration problem in 5G. As the third contribution, we propose a UML-based framework consisting of: (a) a UML5G Service Orchestration Profile (UML5G-SO) that facilitates modeling service orchestration and network slicing for such 5G-based systems, and (b) associated analysis techniques that back the profile, namely logic-based analysis using the USE tool, and exhaustive model checking via UPPAAL. As a final contribution, we propose a tool that integrates UML5G-SO models with UPPAAL, and apply our framework on real use cases of e-Health systems, to provide some experimental evaluation by which we gather useful insights with respect to the framework's practical strengths and weaknesses.Our work in this thesis paves the way towards the development of healthcare assistance systems with assured quality of service.