Concurrency Platforms for Real-Time and Cyber-Physical Systems

Parallel processing is an important way to satisfy the increasingly demanding computational needs of modern real-time and cyber-physical systems, but existing parallel computing technologies primarily emphasize high-throughput and average-case performance metrics, which are largely unsuitable for direct application to real-time, safety-critical contexts. This work contrasts two concurrency platforms designed to achieve predictable worst case parallel performance for soft real-time workloads with millisecond periods and higher. One of these is then the basis for the CyberMech platform, which enables parallel real-time computing for a novel yet representative application called Real-Time Hybrid Simulation (RTHS). RTHS combines demanding parallel real-time computation with real-time simulation and control in an earthquake engineering laboratory environment, and results concerning RTHS characterize a reasonably comprehensive survey of parallel real-time computing in the static context, where the size, shape, timing constraints, and computational requirements of workloads are fixed prior to system runtime. Collectively, these contributions constitute the first published implementations and evaluations of general-purpose concurrency platforms for real-time and cyber-physical systems, explore two fundamentally different design spaces for such systems, and successfully demonstrate the utility and tradeoffs of parallel computing for statically determined real-time and cyber-physical systems

Context-Aware and Secure Workflow Systems

Businesses do evolve. Their evolution necessitates the re-engineering of their existing "business processes”, with the objectives of reducing costs, delivering services on time, and enhancing their profitability in a competitive market. This is generally true and particularly in domains such as manufacturing, pharmaceuticals and education). The central objective of workflow technologies is to separate business policies (which normally are encoded in business logics) from the underlying business applications. Such a separation is desirable as it improves the evolution of business processes and, more often than not, facilitates the re-engineering at the organisation level without the need to detail knowledge or analyses of the application themselves. Workflow systems are currently used by many organisations with a wide range of interests and specialisations in many domains. These include, but not limited to, office automation, finance and banking sector, health-care, art, telecommunications, manufacturing and education. We take the view that a workflow is a set of "activities”, each performs a piece of functionality within a given "context” and may be constrained by some security requirements. These activities are coordinated to collectively achieve a required business objective. The specification of such coordination is presented as a set of "execution constraints” which include parallelisation (concurrency/distribution), serialisation, restriction, alternation, compensation and so on. Activities within workflows could be carried out by humans, various software based application programs, or processing entities according to the organisational rules, such as meeting deadlines or performance improvement. Workflow execution can involve a large number of different participants, services and devices which may cross the boundaries of various organisations and accessing variety of data. This raises the importance of _ context variations and context-awareness and _ security (e.g. access control and privacy). The specification of precise rules, which prevent unauthorised participants from executing sensitive tasks and also to prevent tasks from accessing unauthorised services or (commercially) sensitive information, are crucially important. For example, medical scenarios will require that: _ only authorised doctors are permitted to perform certain tasks, _ a patient medical records are not allowed to be accessed by anyone without the patient consent and _ that only specific machines are used to perform given tasks at a given time. If a workflow execution cannot guarantee these requirements, then the flow will be rejected. Furthermore, features/characteristics of security requirement are both temporal- and/or event-related. However, most of the existing models are of a static nature – for example, it is hard, if not impossible, to express security requirements which are: _ time-dependent (e.g. A customer is allowed to be overdrawn by 100 pounds only up-to the first week of every month. _ event-dependent (e.g. A bank account can only be manipulated by its owner unless there is a change in the law or after six months of his/her death). Currently, there is no commonly accepted model for secure and context-aware workflows or even a common agreement on which features a workflow security model should support. We have developed a novel approach to design, analyse and validate workflows. The approach has the following components: = A modelling/design language (known as CS-Flow). The language has the following features: – support concurrency; – context and context awareness are first-class citizens; – supports mobility as activities can move from one context to another; – has the ability to express timing constrains: delay, deadlines, priority and schedulability; – allows the expressibility of security policies (e.g. access control and privacy) without the need for extra linguistic complexities; and – enjoy sound formal semantics that allows us to animate designs and compare various designs. = An approach known as communication-closed layer is developed, that allows us to serialise a highly distributed workflow to produce a semantically equivalent quasi-sequential flow which is easier to understand and analyse. Such re-structuring, gives us a mechanism to design fault-tolerant workflows as layers are atomic activities and various existing forward and backward error recovery techniques can be deployed. = Provide a reduction semantics to CS-Flow that allows us to build a tool support to animate a specifications and designs. This has been evaluated on a Health care scenario, namely the Context Aware Ward (CAW) system. Health care provides huge amounts of business workflows, which will benefit from workflow adaptation and support through pervasive computing systems. The evaluation takes two complementary strands: – provide CS-Flow’s models and specifications and – formal verification of time-critical component of a workflow

Measurements, Models, Systems and Design

531 s.

Dynamic contracts for verification and enforcement of real-time systems properties

Programa de Doutoramento em Informática (MAP-i) das Universidades do Minho, de Aveiro e do PortoRuntime veri cation is an emerging discipline that investigates methods and tools to enable the veri cation of program properties during the execution of the application. The goal is to complement static analysis approaches, in particular when static veri cation leads to the explosion of states. Non-functional properties, such as the ones present in real-time systems are an ideal target for this kind of veri cation methodology, as are usually out of the range of the power and expressiveness of classic static analyses. Current real-time embedded systems development frameworks lack support for the veri - cation of properties using explicit time where counting time (i.e., durations) may play an important role in the development process. Temporal logics targeting real-time systems are traditionally undecidable. Based on a restricted fragment of Metric temporal logic with durations (MTL-R), we present the proposed synthesis mechanisms 1) for target systems as runtime monitors and 2) for SMT solvers as a way to get, respectively, a verdict at runtime and a schedulability problem to be solved before execution. The later is able to solve partially the schedulability analysis for periodic resource models and xed priority scheduler algorithms. A domain speci c language is also proposed in order to describe such schedulability analysis problems in a more high level way. Finally, we validate both approaches, the rst using empirical scheduling scenarios for unimulti- processor settings, and the second using the use case of the lightweight autopilot system Px4/Ardupilot widely used for industrial and entertainment purposes. The former also shows that certain classes of real-time scheduling problems can be solved, even though without scaling well. The later shows that for the cases where the former cannot be used, the proposed synthesis technique for monitors is well applicable in a real world scenario such as an embedded autopilot ight stack.A verificação do tempo de execução e uma disciplina emergente que investiga métodos e ferramentas para permitir a verificação de propriedades do programa durante a execução da aplicação. O objetivo é complementar abordagens de analise estática, em particular quando a verificação estática se traduz em explosão de estados. As propriedades não funcionais, como as que estão presentes em sistemas em tempo real, são um alvo ideal para este tipo de metodologia de verificação, como geralmente estão fora do alcance do poder e expressividade das análises estáticas clássicas. As atuais estruturas de desenvolvimento de sistemas embebidos para tempo real não possuem suporte para a verificação de propriedades usando o tempo explicito onde a contagem de tempo (ou seja, durações) pode desempenhar um papel importante no processo de desenvolvimento. As logicas temporais que visam sistemas de tempo real são tradicionalmente indecidíveis. Com base num fragmento restrito de MTL-R (metric temporal logic with durations), apresentaremos os mecanismos de síntese 1) para sistemas alvo como monitores de tempo de execução e 2) para solvers SMT como forma de obter, respetivamente, um veredicto em tempo de execução e um problema de escalonamento para ser resolvido antes da execução. O ultimo é capaz de resolver parcialmente a analise de escalonamento para modelos de recursos periódicos e ainda para algoritmos de escalonamento de prioridade fixa. Propomos também uma linguagem especifica de domínio para descrever esses mesmos problemas de analise de escalonamento de forma mais geral e sucinta. Finalmente, validamos ambas as abordagens, a primeira usando cenários de escalonamento empírico para sistemas uni- multi-processador e a segunda usando o caso de uso do sistema de piloto automático leve Px4/Ardupilot amplamente utilizado para fins industriais e de entretenimento. O primeiro mostra que certas classes de problemas de escalonamento em tempo real podem ser solucionadas, embora não seja escalável. O ultimo mostra que, para os casos em que a primeira opção não possa ser usada, a técnica de síntese proposta para monitores aplica-se num cenário real, como uma pilha de voo de um piloto automático embebido.This thesis was partially supported by National Funds through FCT/MEC (Portuguese Foundation for Science and Technology) and co- nanced by ERDF (European Regional Development Fund) under the PT2020 Partnership, within the CISTER Research Unit (CEC/04234); FCOMP-01-0124-FEDER-015006 (VIPCORE) and FCOMP-01-0124-FEDER- 020486 (AVIACC); also by FCT and EU ARTEMIS JU, within project ARTEMIS/0003/2012, JU grant nr. 333053 (CONCERTO); and by FCT/MEC and the EU ARTEMIS JU within project ARTEMIS/0001/2013 - JU grant nr. 621429 (EMC2)

Computer Aided Verification

The open access two-volume set LNCS 11561 and 11562 constitutes the refereed proceedings of the 31st International Conference on Computer Aided Verification, CAV 2019, held in New York City, USA, in July 2019. The 52 full papers presented together with 13 tool papers and 2 case studies, were carefully reviewed and selected from 258 submissions. The papers were organized in the following topical sections: Part I: automata and timed systems; security and hyperproperties; synthesis; model checking; cyber-physical systems and machine learning; probabilistic systems, runtime techniques; dynamical, hybrid, and reactive systems; Part II: logics, decision procedures; and solvers; numerical programs; verification; distributed systems and networks; verification and invariants; and concurrency

Computer Aided Verification

The open access two-volume set LNCS 11561 and 11562 constitutes the refereed proceedings of the 31st International Conference on Computer Aided Verification, CAV 2019, held in New York City, USA, in July 2019. The 52 full papers presented together with 13 tool papers and 2 case studies, were carefully reviewed and selected from 258 submissions. The papers were organized in the following topical sections: Part I: automata and timed systems; security and hyperproperties; synthesis; model checking; cyber-physical systems and machine learning; probabilistic systems, runtime techniques; dynamical, hybrid, and reactive systems; Part II: logics, decision procedures; and solvers; numerical programs; verification; distributed systems and networks; verification and invariants; and concurrency

A methodology for software performance modeling and its application to a border inspection system

It is essential that software systems meet their performance objectives. Many factors affect software performance and it is fundamental to identify those factors and the magnitude of their effects early in the software lifecycle to avoid costly and extensive changes to software design, implementation, or requirements. In the last decade the development of techniques and methodologies to carry out performance analysis in the early stages of the software lifecycle has gained a lot of attention within the research community. Different approaches to evaluate software performance have been developed. Each of them is characterized by a certain software specification and performance modeling notation.;In this thesis we present a methodology for predictive performance modeling and analysis of software systems. We use the Unified Modeling Language (UML) as a software modeling notation and Layered Queuing Networks (LQN) as a performance modeling notation. Our focus is on the definition of a UML to LQN transformation We extend existing approaches by applying the transformation to a different set of UML diagrams, and propose a few extensions to the current UML Profile for Schedulability, Performance, and Time , which we use to annotate UML diagrams with performance-related information. We test the applicability of our methodology to the performance evaluation of a complex software system used at border entry ports to grant or deny access to incoming travelers