Why3-do: The way of harmonious distributed system proofs

We study principles and models for reasoning inductively about properties of distributed systems, based on programmed atomic handlers equipped with contracts. We present the Why3-do library, leveraging a state of the art software verifier for reasoning about distributed systems based on our models. A number of examples involving invariants containing existential and nested quantifiers (including Dijsktra’s self-stabilizing systems) illustrate how the library promotes contract-based modular development, abstraction barriers, and automated proofs.The development of Why3-do was initiated during a visit of the second author to the Toccata team at Inria Saclay-ˆIle-de-France/LRI Univ Paris-Saclay/CNRS and greatly benefited from the team’s hospitality and Why3 expertise. This work is financed by the ERDF – European Regional Development Fund through the North Portugal Regional Operational Programme - NORTE 2020 Programme and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia within project NORTE-01-0145-FEDER-028550 - PTDC/EEI-COM/28550/2017

Verification of distributed algorithms with the Why3 tool

Dissertação de mestrado integrado em Informatics EngineeringNowadays, there currently exist many working program verification tools however, the developed tools are mostly limited to the verification of sequential code, or else of multi-threaded shared-memory programs. Due to the importance that distributed systems and protocols play in many systems, they have been targeted by the program verification community since the beginning of this area. In this sense, they recently tried to create tools capable of deductive verification in the distributed setting (deductive verification techniques offer the highest degree of assurance) and claim to have achieved impressive results. Thus, this dissertation will explore the use of the Why3 deductive verification tool for the verification of dis tributed algorithms. It will comprise the definition of a dedicated Why3library, together with a representative set of case studies. The goal is to provide evidence that Why3 is a privileged tool for such a task, standing at a sweet spot regarding expressive power and practicality.Nos dias de hoje, possuímos diversas ferramentas de verificação, ferramentas essas limitadas à verificação de código sequencial, ou então de programas multi-thread de memória partilhada. Devido à importância que os sistemas e protocolos distribuídos desempenham em muitos sistemas, estes foram alvos por parte da comunidade de verificação de programas desde o início desta área. Neste sentido, recentemente tentaram criar ferramentas capazes de realizar a verificação dedutiva no ambiente distribuído (técnicas de verificação dedutiva que oferecem o mais elevado grau de segurança) e afirmam ter alcançado resultados impressionantes. Assim, esta dissertação irá explorar o uso da ferramenta de verificação dedutiva Why3 com o propósito de verificar algoritmos distribuídos. Irão ser desenvolvidos modos e modelos da biblioteca Why3do, juntamente com um conjunto representativo de casos de estudos. O objetivo é fornecer evidências de que Why3 é uma ferramenta privilegiada para esta tarefa, estando no ponto ideal na relação poder expressivo e praticabilidade.This work is financed by the ERDF – European Regional Development Fund through the North Portugal Regional Operational Programme - NORTE2020 Programme and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia within project NORTE-01-0145-FEDER-028550- PTDC/EEI-COM/28550/2017

From Simple to Complex and Ultra-complex Systems:\ud A Paradigm Shift Towards Non-Abelian Systems Dynamics

Atoms, molecules, organisms distinguish layers of reality because of the causal links that govern their behavior, both horizontally (atom-atom, molecule-molecule, organism-organism) and vertically (atom-molecule-organism). This is the first intuition of the theory of levels. Even if the further development of the theory will require imposing a number of qualifications to this initial intuition, the idea of a series of entities organized on different levels of complexity will prove correct. Living systems as well as social systems and the human mind present features remarkably different from those characterizing non-living, simple physical and chemical systems. We propose that super-complexity requires at least four different categorical frameworks, provided by the theories of levels of reality, chronotopoids, (generalized) interactions, and anticipation

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