Progetto e sviluppo di un verificatore efficiente del bytecode java

La tecnologia Java Card costituisce il punto di contatto tra il linguaggio di programmazione Java e l’ambiente operativo di sistemi con un numero limitato di risorse. Java è un linguaggio interpretato: il codice assemblato viene eseguito su una macchina virtuale, la Java Virtual Machine (JVM), che garantisce l’indipendenza del codice dalla particolare piattaforma hardware/software. La JVM gioca inoltre un ruolo centrale per quanto riguarda la sicurezza e la correttezza del codice eseguito: la sicurezza è legata a meccanismi che controllano i diritti di accesso a informazioni e funzionalità, la correttezza garantisce invece che i meccanismi di sicurezza non vengano by-passati. Il “verificatore” è il modulo della JVM che analizza la correttezza del codice: la tecnologia corrente non consente l’implementazione di un verificatore “standard” direttamente on-card perché il processo di verifica richiede in genere un numero elevato di risorse. In questa tesi viene proposto un verificatore che ottimizza l’utilizzo delle risorse attraverso una analisi del grafo di flusso del codice: l’idea di base è di scomporre il codice in blocchi indipendenti e di rendere dinamica l’allocazione delle risorse applicando l’algoritmo di verifica ad ogni blocco. Le risorse da allocare sono solo quelle necessarie alla verifica di un sotto-insieme di istruzioni: la complessità del processo di verifica diminuisce e la realizzazione di un verificatore on-card diventa un obiettivo raggiungibile. E’ stato inoltre sviluppato un prototipo a partire dal codice di un verificatore open-source

A PVS-Simulink Integrated Environment for Model-Based Analysis of Cyber-Physical Systems

This paper presents a methodology, with supporting tool, for formal modeling and analysis of software components in cyber-physical systems. Using our approach, developers can integrate a simulation of logic-based specifications of software components and Simulink models of continuous processes. The integrated simulation is useful to validate the characteristics of discrete system components early in the development process. The same logic-based specifications can also be formally verified using the Prototype Verification System (PVS), to gain additional confidence that the software design complies with specific safety requirements. Modeling patterns are defined for generating the logic-based specifications from the more familiar automata-based formalism. The ultimate aim of this work is to facilitate the introduction of formal verification technologies in the software development process of cyber-physical systems, which typically requires the integrated use of different formalisms and tools. A case study from the medical domain is used to illustrate the approach. A PVS model of a pacemaker is interfaced with a Simulink model of the human heart. The overall cyber-physical system is co-simulated to validate design requirements through exploration of relevant test scenarios. Formal verification with the PVS theorem prover is demonstrated for the pacemaker model for specific safety aspects of the pacemaker design

Modeling communication network requirements for an integrated clinical environment in the Prototype Verification System

Health care practices increasingly rely on complex technological infrastructure, and new approaches to the integration of information and communication technology in those practices lead to the development of such concepts as integrated clinical environments and smart intensive care units. These concepts refer to hospital settings where therapy relies heavily on inter-operating medical devices, supervised by clinicians assisted by advanced monitoring and co-ordinating software. In order to ensure safety and effectiveness of patient care, it is necessary to specify the requirements of such socio-technical systems in the most rigorous and precise way. This paper presents an approach to the formalization of system requirements for communication networks deployed in integrated clinical environment, based on the higher-order logic language of a theorem-proving environment, the Prototype Verification System

Towards a Formalization of System Requirements for an Integrated Clinical Environment

Interoperability of medical devices, and their interface to clinicians and patients, are critical issues for the safety and effectiveness of patient care. Ongoing efforts strive at establishing standards for integrated clinical environments, which may connect and co-ordinate several medical devices and interface them to patients, clinicians, and hospital information systems. In this paper, an approach to the formalization of system requirements for an integrated clinical environment is presented. The formalization relies on the higher-order logic language of the Prototype Verification System

PVSio-web: a tool for rapid prototyping device user interfaces in PVS

We present PVSio-web which extends the simulation component of the PVS proof system with functionalities for rapid prototyping device user interfaces. The tool presents itself as a classic image-editing environment with functionalities such as area selection and hyperlink creation, thus reducing the barriers that prevent non-experts in formal methods from using PVS. Designers load a picture of the layout of the device user interface under development, specify interactive areas over the layout, and link them to a PVS specification. They can then explore the behaviour of the formal user interface specification through point-and-click interactions. The architecture of the tool is general, and can be used as the basis for extending other verification tools. A demonstration of the capabilities of PVSio-web is presented through an example based on a commercial medical device user interface. Our ultimate aim is to promote and facilitate the use of formal verification tools when developing device user interfaces

Modelling Distributed Cognition Systems in PVS

We report on our efforts to formalise DiCoT, an informal structured approach for analysing complex work systems, such as hospital and day care units, as distributed cognition systems. We focus on DiCoT's information flow model, which describes how information is transformed and propagated in the system. Our contribution is a set of generic models for the specification and verification system PVS. The developed models can be directly mapped to the informal descriptions adopted by human-computer interactions experts. The models can be verified against properties of interest in the PVS theorem prover. Also, the same models can be simulated, thus facilitating analysts to engage with stakeholders when checking the correctness of the model. We trial our ideas on a case study based on a real-world medical system

Verification templates for the analysis of user interface software design

The paper describes templates for model-based analysis of usability and safety aspects of user interface software design. The templates crystallize general usability principles commonly addressed in user-centred safety requirements, such as the ability to undo user actions, the visibility of operational modes, and the predictability of user interface behavior. These requirements have standard forms across different application domains, and can be instantiated as properties of specific devices. The modeling and analysis process is carried out using the Prototype Verification System (PVS), and is further facilitated by structuring the specification of the device using a format that is designed to be generic across interactive systems. A concrete case study based on a commercial infusion pump is used to illustrate the approach. A detailed presentation of the automated verification process using PVS shows how failed proof attempts provide precise information about problematic user interface software features.This work has been funded by the EPSRC research grant EP/G059063/1: CHI+ MED (Computer-Human Interaction for Medical Devices). We are grateful to Harold Thimbleby's team at Swansea University, part of the CHI+ MED project, and especially Patrick Oladimeji who developed the infusion pump simulation that helped us develop the models. We also thank the anonymous reviewers for valuable feedback. Jose C. Campos and Paolo Masci were funded by project NORTE-01-0145-FEDER-000016, financed by the North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF)

Developing and Verifying User Interface Requirements for Infusion Pumps: A Refinement Approach

It is common practice in the description of criteria for the acceptable safety of systems for the regulator to describe safety requirements that should be satisfied by the system. These requirements are typically described precisely but in natural language and it is often unclear how the regulator can be assured that the given requirements are satisfied. This paper is concerned with a rigorous refinement process that demonstrates that a precise requirement is satisfied by the specification of a given device. It focuses on a particular class of requirements that relate to the user interface of the device. For user interface requirements, refinement is made more complex by the fact that systems can use different interaction devices that have very different characteristics. The described refinement process recognises an input/output hierarchy

Layers, resources and property templates in the specification and analysis of two interactive systems

The paper briefly explores a layered approach to the analysis of two interactive systems (Nuclear Control and Air Traffic Control), indicating how the analysis enables exploration of the particular features emphasised by the use cases relating to the examples. These features relate to the interactive behaviour of the systems. To facilitate the analysis, property templates are proposed as heuristics for developing appropriate requirements for the respective user interfaces.Jose Creissac Campos and Michael Harrison were funded by ´ project ref. NORTE-07-0124-FEDER-000062, co-financed by the North Portugal Regional Operational Programme (ON.2 O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), and by national funds, through the Portuguese foundation for science and technology (FCT). Paul Curzon, Michael Harrison and Paolo Masci were funded by the CHI+MED project: Multidisciplinary Computer Human Interaction Research for the design and safe use of interactive medical devices project, UK EPSRC Grant Number EP/G059063/1.info:eu-repo/semantics/publishedVersio