A formally verified compiler back-end

This article describes the development and formal verification (proof of semantic preservation) of a compiler back-end from Cminor (a simple imperative intermediate language) to PowerPC assembly code, using the Coq proof assistant both for programming the compiler and for proving its correctness. Such a verified compiler is useful in the context of formal methods applied to the certification of critical software: the verification of the compiler guarantees that the safety properties proved on the source code hold for the executable compiled code as well

Second CLIPS Conference Proceedings, volume 1

Topics covered at the 2nd CLIPS Conference held at the Johnson Space Center, September 23-25, 1991 are given. Topics include rule groupings, fault detection using expert systems, decision making using expert systems, knowledge representation, computer aided design and debugging expert systems

Validating a neural network-based online adaptive system

Neural networks are popular models used for online adaptation to accommodate system faults and recuperate against environmental changes in real-time automation and control applications. However, the adaptivity limits the applicability of conventional verification and validation (V&V) techniques to such systems. We investigated the V&V of neural network-based online adaptive systems and developed a novel validation approach consisting of two important methods. (1) An independent novelty detector at the system input layer detects failure conditions and tracks abnormal events/data that may cause unstable learning behavior. (2) At the system output layer, we perform a validity check on the network predictions to validate its accommodation performance.;Our research focuses on the Intelligent Flight Control System (IFCS) for NASA F-15 aircraft as an example of online adaptive control application. We utilized Support Vector Data Description (SVDD), a one-class classifier to examine the data entering the adaptive component and detect potential failures. We developed a decompose and combine strategy to drastically reduce its computational cost, from O(n 3) down to O( n32 log n) such that the novelty detector becomes feasible in real-time.;We define a confidence measure, the validity index, to validate the predictions of the Dynamic Cell Structure (DCS) network in IFCS. The statistical information is collected during adaptation. The validity index is computed to reflect the trustworthiness associated with each neural network output. The computation of validity index in DCS is straightforward and efficient.;Through experimentation with IFCS, we demonstrate that: (1) the SVDD tool detects system failures accurately and provides validation inferences in a real-time manner; (2) the validity index effectively indicates poor fitting within regions characterized by sparse data and/or inadequate learning. The developed methods can be integrated with available online monitoring tools and further generalized to complete a promising validation framework for neural network based online adaptive systems

Influence of deficiencies in traffic control devices in crashes on two-lane rural roads

[EN] One of the main objectives of all public administrations is reducing traffic crashes. To this end, Road Safety Inspections (RSI) stand out as a key measure. Signaling roads is one of the foremost tasks of RSI. A road that is improperly or poorly signaled can lead to incorrect placement or maneuvers of vehicles and ambiguous situations that can increase the risk of crashes. This paper analyses the relationship between road crashes in two-lane rural highways and certain deficiencies in signaling. The results show that deficiencies such as "incomplete removal of road works markings" or "no guide sign or in incorrect position" are the ones' associated with a higher probability of crashes in two-lane rural highways. In view of these results, governmental agencies should verify that the original conditions of a highway are re-established after any construction work is completed. They should also continuously follow up on the signaling of this type of highway in order to maintain optimal conditions. (C) 2016 Elsevier Ltd. All rights reserved.The authors would like to acknowledge FEDER funding by the European Union for financial support via project "Analisis de la relacion entre Elementos Susceptibles de Mejora, Accidentes y TCA" of the "Programa Operativo FEDER de Andalucia 2007-2013". We also thank the Public Works Agency and Regional Ministry of Public Works and Housing of the Regional Government of Andalusia. The authors are grateful to the Spanish General Directorate of Traffic (DGT) for providing the data necessary for this research. Griselda Lopez wishes to express her acknowledgement to the regional ministry of Economy, Innovation and Science of the regional government of Andalusia (Spain) for a scholarship to train teachers and researchers in Deficit Areas.López-Maldonado, G.; De Oña, J.; Garach, L.; Baena-Ruiz, L. (2016). Influence of deficiencies in traffic control devices in crashes on two-lane rural roads. Accident Analysis & Prevention. 96:130-139. https://doi.org/10.1016/j.aap.2016.08.008S1301399

Human Rating the Orion Parachute System

Human rating begins with design. Converging on the requirements and identifying the risks as early as possible in the design process is essential. Understanding of the interaction between the recovery system and the spacecraft will in large part dictate the achievable reliability of the final design. Component and complete system full-scale flight testing is critical to assure a realistic evaluation of the performance and reliability of the parachute system. However, because testing is so often difficult and expensive, comprehensive analysis of test results and correlation to accurate modeling completes the human rating process. The National Aeronautics and Space Administration (NASA) Orion program uses parachutes to stabilize and decelerate the Crew Exploration Vehicle (CEV) spacecraft during subsonic flight in order to deliver a safe water landing. This paper describes the approach that CEV Parachute Assembly System (CPAS) will take to human rate the parachute recovery system for the CEV

Applying Formal Methods to Networking: Theory, Techniques and Applications

Despite its great importance, modern network infrastructure is remarkable for the lack of rigor in its engineering. The Internet which began as a research experiment was never designed to handle the users and applications it hosts today. The lack of formalization of the Internet architecture meant limited abstractions and modularity, especially for the control and management planes, thus requiring for every new need a new protocol built from scratch. This led to an unwieldy ossified Internet architecture resistant to any attempts at formal verification, and an Internet culture where expediency and pragmatism are favored over formal correctness. Fortunately, recent work in the space of clean slate Internet design---especially, the software defined networking (SDN) paradigm---offers the Internet community another chance to develop the right kind of architecture and abstractions. This has also led to a great resurgence in interest of applying formal methods to specification, verification, and synthesis of networking protocols and applications. In this paper, we present a self-contained tutorial of the formidable amount of work that has been done in formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial

Automatic rule verification for digital building permits

Dissertação de mestrado em Modelação de Informação na Construção de Edifícios BIM A+O sector da construção está a enfrentar grandes mudanças nas exigências do cliente e do mercado, empurrando para a transformação digital e para uma indústria orientada para os dados. Os governos tomaram parte ativa nesta mudança, apoiando a digitalização de processos como o das licenças de construção, introduzindo a utilização de modelos de informação de construção (BIM). A investigação sobre a digitalização do licenciamento municipal de construções mostrou grandes avanços no que diz respeito à extração de regras de forma interpretável e à automatização de verificações; contudo, a conciliação entre as definições semânticas do modelo de construção e os conceitos definidos nos regulamentos está ainda em discussão. Além disso, a validação da acuidade das informações incluídas nos modelos de construção relativamente às definições do regulamento é importante para garantir a qualidade ao longo do processo de licença de construção. Esta dissertação visa propor um fluxo de trabalho híbrido para verificar a informação extraída explicitamente do modelo BIM e a informação implicitamente derivada das relações entre elementos, seguindo as disposições contidas nos regulamentos no contexto de Portugal. Com base em alguma revisão de literatura, foi proposto um novo processo, e foi desenvolvido um código Python utilizando a biblioteca IfcOpenshell para apoiar a automatização do processo de verificação, tradicionalmente realizada por técnicos nos gabinetes de licenciamento municipal. Os elementos desenvolvidos neste documento foram comprovados num estudo de caso, demonstrando que a validação híbrida pode ajudar a detetar erros de modelação e melhorar a acuidade da informação durante a apresentação inicial de modelos para um processo de licença de construção. Os resultados indicam que a inclusão de uma validação automática do modelo contra definições regulamentares pode ser introduzida para melhorar o grau de certeza da qualidade da informação contida no Modelo de Informação, além disso, a proposta de métodos que produzem resultados a partir de informação implícita pode alargar as capacidades do esquema IFC. Contudo, os esquemas desenvolvidos neste trabalho estão ainda em constante revisão e desenvolvimento e têm limitações de aplicabilidade em relação a certas classes do IFC.The construction sector is facing major changes in the client and market requirements, pushing towards the digital transformation and a data driven industry. Governments have taken an active part in this change by supporting the digitalization of processes such as the one for building permits by introducing the use of building information models (BIM). The research on the digitalization of the building permit has shown great advancements in regarding the rule extraction in interpretable ways and the automation of the verification; however, the conciliation between the building model semantic definitions and the concepts defined in the regulations is still in discussion. Moreover, the validation of the correctness of the information included in building models regarding the regulation definitions is important to guarantee the quality along the digital building permit process. This dissertation aims to propose a hybrid workflow to check the information extracted explicitly from the BIM model and the information implicitly derived from relationships between elements by following the provisions contained in the regulations in the context of Portugal. Based on some context and literature review, a process reengineering was proposed, and a Python code was developed using the IfcOpenShell library to support the automation of the verification process, traditionally carried out by technicians in the building permit offices. The elements developed in this document were proven in a case-study, demonstrating that the hybrid validation can help to detect modelling errors and improve the certainty of correctness of information during the initial submission of models for a building permit process. The results indicate that the inclusion of an automated validation of the model against regulation definitions can be introduced to improve the degree of certainty of the quality of the information contained in the Building Information Model, moreover the proposal of methods that produce results from implicit information can extend the capabilities of the IFC schema. However, the scripts developed in this work are still under constant review and development and have limitations of applicability in relation to certain IFC classes.Erasmus Mundus Joint Master Degree Programme – ERASMUS

Defining procedures and simulation tools to test high levels of automation for cars in realistic traffic, driving and boundary conditions

Il crescente livello di automazione nella guida dei veicoli su gomma rende sempre più complesse e articolate le procedure di testing e validazione dei dispositivi. La tendenza alla realizzazione di sistemi che sostituiscano il guidatore in tutto o in parte, determina un cambiamento paradigmatico nell'ambito della validazione, la quale non può più occuparsi esclusivamente del test del corretto funzionamento del dispositivo da validare, ma dovrà testare le logiche di guida e le "scelte" che opera al variare dei contesti. Come ampiamente evidenziato nella letteratura scientifica di settore1 i processi di validazione rappresenteranno il più grande ostacolo alla realizzazione e messa in produzione dei sistemi di quarto e quinto livello SAE2 di automazione. Numerose ricerche hanno dimostrato3 che il testing su strada non rappresenta una soluzione che possa dare risultati attendibili in tempi sufficientemente brevi, ma a tutt'oggi non esistono software sufficientemente complessi da realizzare simulazioni che tengano conto di tutte le variabili necessarie. La ricerca intende definire le corrette procedure di testing di veicoli ad elevato grado di automazione in condizioni di traffico realistiche, avvalendosi di software di simulazione specifici di ogni settore coinvolto nel processo, realizzando uno strumento di testing integrato sufficientemente efficace