From Temporal Models to Property-Based Testing

This paper presents a framework to apply property-based testing (PBT) on top of temporal formal models. The aim of this work is to help software engineers to understand temporal models that are presented formally and to make use of the advantages of formal methods: the core time-based constructs of a formal method are schematically translated to the BeSpaceD extension of the Scala programming language. This allows us to have an executable Scala code that corresponds to the formal model, as well as to perform PBT of the models functionality. To model temporal properties of the systems, in the current work we focus on two formal languages, TLA+ and FocusST.Comment: Preprint. Accepted to the 12th International Conference on Evaluation of Novel Approaches to Software Engineering (ENASE 2017). Final version published by SCITEPRESS, http://www.scitepress.or

Formal Analysis and Redesign of a Neural Network-Based Aircraft Taxiing System with VerifAI

We demonstrate a unified approach to rigorous design of safety-critical autonomous systems using the VerifAI toolkit for formal analysis of AI-based systems. VerifAI provides an integrated toolchain for tasks spanning the design process, including modeling, falsification, debugging, and ML component retraining. We evaluate all of these applications in an industrial case study on an experimental autonomous aircraft taxiing system developed by Boeing, which uses a neural network to track the centerline of a runway. We define runway scenarios using the Scenic probabilistic programming language, and use them to drive tests in the X-Plane flight simulator. We first perform falsification, automatically finding environment conditions causing the system to violate its specification by deviating significantly from the centerline (or even leaving the runway entirely). Next, we use counterexample analysis to identify distinct failure cases, and confirm their root causes with specialized testing. Finally, we use the results of falsification and debugging to retrain the network, eliminating several failure cases and improving the overall performance of the closed-loop system.Comment: Full version of a CAV 2020 pape

Characterization of graphite polyurethanes composite from renewable based oils

This thesis aims to evaluate the characterization of graphite polyurethane composite from renewable based oils. Virgin cooking oil (VCO) as a renewable resource is the main substance in fabricating the renewable polyurethane (PU) and its graphite as called polyurethane graphite (PG). The fabricating sample have two methods that is open casting and heat press method. PU and PG with different percentage of graphite as filler were investigated for structural, morphological, physical and mechanical properties that going through a several testing including Optical Microscope (OM), Scanning Electron Microscope (SEM), Ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), Density Test, Tensile test and cross-link density. The renewable polyurethane is namely as PU and polyurethane graphite is namely as PG2, PG4, PG6, PG8, PG10 with subscript numbers indicate the weight loading of graphite content was varied in the renewable polyurethane from 2, 4, 6, 8, and 10wt%. The result of SEM and OM showed that the graphite particles are randomly distributed and homogeneously scattered well in the PU due to interconnected interface within the matrix of polymeric composites. UV- Vis technique is used to characterize the absorption, transmission and reflectivity of the PU and PG’s otherwise the FT-IR is used for determine the composition and characterize the polymer structure of PU and PG’s. As expected, the mechanical properties of composites proven that the addition of graphite can change the matrix properties of PU to improve modulus and consequent lowered the tan delta with respected of increasing the temperature. The calculated cross-linked density of PU and PG composites revealed the increment of graphite particle loading gives highest result of cross-linking and this is due to the PG10 is the highest graphite content and the highest value of storage modulus, highest value of tensile strength and the highest value of young modulus. Therefore, the result shows the renewable polymer graphite composite is suitable to be used in various composites applications

Towards Model Checking Executable UML Specifications in mCRL2

We describe a translation of a subset of executable UML (xUML) into the process algebraic specification language mCRL2. This subset includes class diagrams with class generalisations, and state machines with signal and change events. The choice of these xUML constructs is dictated by their use in the modelling of railway interlocking systems. The long-term goal is to verify safety properties of interlockings modelled in xUML using the mCRL2 and LTSmin toolsets. Initial verification of an interlocking toy example demonstrates that the safety properties of model instances depend crucially on the run-to-completion assumptions

Provably Correct Control-Flow Graphs from Java Programs with Exceptions

We present an algorithm to extract flow graphs from Java bytecode, focusing on exceptional control flows. We prove its correctness, meaning that the behaviour of the extracted control-flow graph is an over-approximation of the behaviour of the original program. Thus any safety property that holds for the extracted control-flow graph also holds for the original program. This makes control-flow graphs suitable for performing different static analyses. For precision and efficiency, the extraction is performed in two phases. In the first phase the program is transformed into a BIR program, where BIR is a stack-less intermediate representation of Java bytecode; in the second phase the control-flow graph is extracted from the BIR representation. To prove the correctness of the two-phase extraction, we also define a direct extraction algorithm, whose correctness can be proven immediately. Then we show that the behaviour of the control-flow graph extracted via the intermediate representation is an over-approximation of the behaviour of the directly extracted graphs, and thus of the original program