Verification Conditions Research Articles

Extending Liquid Types to Arrays

A liquid type is an ordinary Hindley-Milner type annotated with a logical predicate that states the properties satisfied by the elements of that type. Liquid types are a powerful tool for program verification, as programmers can use them to specify pre- and post conditions of their programs, whereas the predicates of intermediate variables and auxiliary functions are inferred automatically. Type inference is feasible in this context, as the logical predicates within liquid types are constrained to a quantifier-free logic to maintain decidability. In this article, we extend liquid types by allowing them to contain quantified properties on arrays so that they can be used to infer invariants on array-related programs (e.g., implementations of sorting algorithms). Although quantified logic is, in general, undecidable, we restrict properties on arrays to a decidable subset introduced by Bradley et al. We describe in detail the extended type system, the verification condition generator, and the iterative weakening algorithm for inferring invariants. After proving the correctness and completeness of these two algorithms, we apply them to find invariants on a set of algorithms involving array manipulations.

Problems of implementation of the principle of legal certainty in the framework of judicial verification activities in the civil process

««Вестник Санкт-Петербургского университета. Право» — международный научно-теоретический рецензируемый журнал, публикующий материалы в следующих рубриках: Публичное и частное право: прикладные исследования Криминология Криминалистика Судебная экспертиза Исследования права с позиций социальных и гуманитарных (неюридических) наук Правовая жизнь: научно-практические заключения, комментарии и обзоры Сравнительное право Зарубежное право

IDENTIFICATION OF A CYCLICAL COMPONENT IN THE\r\nSOCIO-ECONOMIC DEVELOPMENT OF AZERBAIJAN

Ponte Academic JournalOct 2020, Volume 76, Issue 10 ECONOMETRIC ANALYSISOF AZERBAIJAN\'S GDP USING SINGULAR SPECTRAL ANALYSIS (SSA)Author(s): Esmira AhmadovaJ. Ponte - Oct 2020 - Volume 76 - Issue 10 doi: 10.21506/j.ponte.2020.10.16 Abstract:This article focuses on a brief critical analysis of the theory of Singular Spectrum Analysis and the problem of distinguishing cyclic components from a general dynamics of economic situation. As a solution to this problem the asynchronous harmonic analysis algorithm based on spectrum analysis and decomposition filtering algorithm has been proposed. This research is based on fundamental works by foreign scientists and research workers. The aim of this research is to identify and evaluate the cyclic component and prospects of social and economic development of Azerbaijan based on the analysis of the most important GDP indicator. As a result of the research, several economic models have been designed and important cyclic dependencies have been identified. Also, an econometric analysis of models with relevant conclusions has been performed. Calculations and graphs have been made by free software, i.e. the statistical environment R, which is one of the most dynamically developing programs in its class. In the course of the study, the main parameters, general trends, seasonal and cyclical components of Azerbaijan's GDP for the period of 22 years, between 1997 to 2019 have been identified. The comprehensive econometric tests carried out during the research showed that the designed econometric models correspond to all basic ideas of econometric analysis including the conditions of specification, parameterization and verification, and prove to be reasonable for the real economic situation in the country. The findings of the research, with regard to their practical significance, can be successfully applied to analyse and predict the socio-economic development potential during the diversification of the economy of Azerbaijan. The results, suggestions and recommendations obtained in this research can be used in shortterm and mid-term planning of the main indicators of social and economic development of Azerbaijan. Download full text:Check if you have access through your login credentials or your institution Username Password

Архитектура системы дедуктивной верификации машинного кода

In recent years, ISP RAS has been developing a system for machine (binary) code deductive verification. The motivation is rather clear: modern compilers, such as GCC and Clang/LLVM, are not free of bugs; thereby, it is not superfluous (at least for safety- and security-critical components) to check the correctness of the generated code. The key feature of the suggested approach is the ability to reuse source-code-level formal specifications (pre- and postconditions, loop invariants, lemma functions, etc.) at the machine code level. The tool is highly automated: provided that the target instruction set is formalized, it disassembles the machine code, extracts its semantics, adapts the high-level specifications, and generates the verification conditions. The system utilizes a number of third-party components including a source code analyzer (Frama-C), a machine code analyzer (MicroTESK), and an SMT solver (CVC4). The modular design enables replacing one component with another when switching an input format and/or a verification engine. In this paper, we discuss the tool architecture, describe our implementation, and present a case study on verifying the memset C library function.

System FR: formalized foundations for the stainless verifier

We present the design, implementation, and foundation of a verifier for higher-order functional programs with generics and recursive data types. Our system supports proving safety and termination using preconditions, postconditions and assertions. It supports writing proof hints using assertions and recursive calls. To formalize the soundness of the system we introduce System FR, a calculus supporting System F polymorphism, dependent refinement types, and recursive types (including recursion through contravariant positions of function types). Through the use of sized types, System FR supports reasoning about termination of lazy data structures such as streams. We formalize a reducibility argument using the Coq proof assistant and prove the soundness of a type-checker with respect to call-by-value semantics, ensuring type safety and normalization for typeable programs. Our program verifier is implemented as an alternative verification-condition generator for the Stainless tool, which relies on the Inox SMT-based solver backend for automation. We demonstrate the efficiency of our approach by verifying a collection of higher-order functional programs comprising around 14000 lines of polymorphic higher-order Scala code, including graph search algorithms, basic number theory, monad laws, functional data structures, and assignments from popular Functional Programming MOOCs.

Decision support system for assessing the state of atmospheric air under inaccurate input data

The article deals with the design of a decision support system structure for assessing the state of atmospheric air under inaccurate input data. The methodologies of constructing information systems, their advantages and disadvantages when applying to the design of a decision support system are considered. The data streams are investigated and the corresponding diagram is proposed on the basis of them. The structure of the system as a whole is proposed, as well as the construction of a model base as the part of a complex system. Different questions related to functioning of the system are considered such as the organization of the data exchange, definition of conditions of applicability and verification of models, synchronization of work of various parts of the system.

Theorem and Algorithm Checking for Courses on Logic and Formal Methods

The RISC Algorithm Language (RISCAL) is a language for the formal modeling of theories and algorithms. A RISCAL specification describes an infinite class of models each of which has finite size; this allows to fully automatically check in such a model the validity of all theorems and the correctness of all algorithms. RISCAL thus enables us to quickly verify/falsify the specific truth of propositions in sample instances of a model class before attempting to prove their general truth in the whole class: the first can be achieved in a fully automatic way while the second typically requires our assistance. RISCAL has been mainly developed for educational purposes. To this end this paper reports on some new enhancements of the tool: the automatic generation of checkable verification conditions from algorithms, the visualization of the execution of procedures and the evaluation of formulas illustrating the computation of their results, and the generation of Web-based student exercises and assignments from RISCAL specifications. Furthermore, we report on our first experience with RISCAL in the teaching of courses on logic and formal methods and on further plans to use this tool to enhance formal education.

Optimal acceptance sampling for modules F and F1 of the European Measuring Instruments Directive

ABSTRACTAcceptance sampling plans offered by ISO 2859-1 are far from optimal under the conditions for statistical verification in modules F and F1 as prescribed by Annex II of the Measuring Instruments Directive (MID) 2014/32/EU, resulting in sample sizes that are larger than necessary. An optimised single-sampling scheme is derived, both for large lots using the binomial distribution and for finite-sized lots using the exact hypergeometric distribution, resulting in smaller sample sizes that are economically more efficient while offering the full statistical protection required by the MID.

A verified, efficient embedding of a verifiable assembly language

High-performance cryptographic libraries often mix code written in a high-level language with code written in assembly. To support formally verifying the correctness and security of such hybrid programs, this paper presents an embedding of a subset of x64 assembly language in F* that allows efficient verification of both assembly and its interoperation with C code generated from F*. The key idea is to use the computational power of a dependent type system's type checker to run a verified verification-condition generator during type checking. This allows the embedding to customize the verification condition sent by the type checker to an SMT solver. By combining our proof-by-reflection style with SMT solving, we demonstrate improved automation for proving the correctness of assembly-language code. This approach has allowed us to complete the first-ever proof of correctness of an optimized implementation of AES-GCM, a cryptographic routine used by 90% of secure Internet traffic.

Pretend synchrony: synchronous verification of asynchronous distributed programs

We present pretend synchrony , a new approach to verifying distributed systems, based on the observation that while distributed programs must execute asynchronously, we can often soundly treat them as if they were synchronous when verifying their correctness. To do so, we compute a synchronization , a semantically equivalent program where all sends, receives, and message buffers, have been replaced by simple assignments, yielding a program that can be verified using Floyd-Hoare style Verification Conditions and SMT. We implement our approach as a framework for writing verified distributed programs in Go and evaluate it with four challenging case studies— the classic two-phase commit protocol, the Raft leader election protocol, single-decree Paxos protocol, and a Multi-Paxos based distributed key-value store. We find that pretend synchrony allows us to develop performant systems while making verification of functional correctness simpler by reducing manually specified invariants by a factor of 6, and faster , by reducing checking time by three orders of magnitude.

Method of Solving Problem of Conditional Optimization on Combinatorial Set of Arrangements

The paper considered a formulated optimization problem on a combinatorial set of arrangements and suggested a method for its solution taking into account satisfaction of conditions imposed on gains of restrictions and objective function. The method consists of three steps. The first step constructs normalization and compliance matrices which provide transformation of arrangements set elements to a necessary form for the objective function and the given restrictions. The second step consists in finding the first support solution taking into account the arrangements set property. It is worth noting that to find the first support solution it is sufficient to calculate gains of restrictions. If the feasible solution satisfies presented inequalities, the initial data are fixed to be the verification conditions for the next improved solution. The value of objective function is determined by calculating objective function gains without the need to calculate the entire previous function. The third step provides finding the optimal solution at direct improvement of the obtained support solution. This step formulated sufficient and necessary conditions to search for the optimal solution, considered numerical examples of searching for externa of functions on the arrangements set and also presented numerical experiment for the case of |Ak3| with growing number of sample units of the arrangements set (k). It is also worth noting that the number of steps of searching for the optimal solution does not significantly increase at a sharply increased number of elements of arrangements set. Analyzing the indicator of percentage ratio of the considered points number when searching for the optimal solution and the number of elements of arrangements set it should be noted its considerable reduction that indicates to efficiency of the proposed method. So this method application allows us to find the function extremum on the set of arrangements over the finite number of steps.

Probabilistic Sequential Prediction of Cutting Force Using Kienzle Model in Orthogonal Turning Process

Probabilistic sequential prediction of cutting forces is performed applying Bayesian inference to Kienzle force model. The model uncertainties are quantified using the Metropolis algorithm of the Markov chain Monte Carlo (MCMC) approach. Prior probabilities are established and posteriors of the models parameters and force predictions are completed using the results of orthogonal turning experiments. Two types of tools with chamfer (rake) angles of 0 deg and −10 deg are tested under various cutting speed and feed per revolution values. First, Bayesian inference is applied to two force models, Merchant and Kienzle, to investigate the cutting force prediction at the low feed values for the 0 deg rake angle tool. Second, the results of the posteriors of the Kienzle model parameters are used as prior probabilities of the −10 deg rake angle tool. The simulation results of the 0 deg and −10 deg tool rake angle are compared with the experiments which are obtained under other cutting conditions for model verification. Maximum prediction errors of 7% and 9% are reported for the tangential and feed forces, respectively. This indicates a good capability of the Bayesian inference for model parameter identification and cutting force prediction considering the inherent uncertainty and minimum input experimental data.

Safety Verification of Nonlinear Hybrid Systems Based on Bilinear Programming

In safety verification of hybrid systems, barrier certificates are generated by solving the verification conditions derived from non-negative representations of different types. This paper presents a new computational method, sequential linear programming projection, for directly solving the set of verification conditions represented by the Krivine–Vasilescu–Handelman’s positivstellensatz. The key idea is to decompose it into two successive optimization problems that refine the desired barrier certificate and those undetermined multipliers, respectively, and solve it in an iterative scheme. The most important benefit of the proposed approach lies in that it is much more effective than the LP relaxation method in producing real barrier certificates, and possesses a much lower computational complexity than the popular sum of square relaxation methods, which is demonstrated by the theoretical analysis on complexity and the experiment on a set of examples gathered from the literature.

The Automation of C Program Verification by Symbolic Method of Loop Invariants Elimination

During deductive verification of programs written in imperative languages, the generation and proof of verification conditions corresponding to loops can cause difficulties, because each one must be provided with an invariant whose construction is often a challenge. As a rule, the methods of invariant synthesis are heuristic ones. This impedes its application. An alternative is the symbolic method of loop invariant elimination suggested by V.A. Nepomniaschy in 2005. Its idea is to represent a loop body in a form of special replacement operation under certain constraints. This operation expresses loop effect in a symbolic form and allows to introduce an inference rule which uses no invariants in axiomatic semantics. This work represents the further development of this method. It extends the mixed axiomatic semantics method suggested for C-light program verification. This extension includes the verification method of iterations over changeable arrays possibly with loop exit in C-light programs. The method contains the inference rule for iterations without loop invariants. This rule was implemented in verification conditions generator which is a part of the automated system of C-light program verification. To prove verification conditions automatically in ACL2, two algorithms were developed and implemented. The first one automatically generates the replacement operation in ACL2 language, the second one automatically generates auxiliary lemmas which allow to prove the obtained verification conditions in ACL2 successfully in automatic mode. An example which illustrates the application of the mentioned methods is described.

Numerical simulation of complex hexagonal structures to predict drop behavior under submerged and fluid flow conditions

Abstract This study simulated a control rod assembly (CRA), which is a part of reactor shutdown systems, in immersed and fluid flow conditions. The CRA was inserted into the reactor core within a predetermined time limit under normal and abnormal operating conditions, and the CRA (which consists of complex geometric shapes) drop behavior is numerically modeled for simulation. A full-scale prototype CRA drop test is established under room temperature and water-fluid conditions for verification and validation. This paper describes the details of the numerical modeling and analysis results of the several conditions. Results from the developed numerical simulation code are compared with the test results to verify the numerical model and developed computer code. The developed code is in very good agreement with the test results and this numerical analysis model and method may replace the experimental and CFD method to predict the drop behavior of CRA.

Enhancing multi-factor cheating prevention in visual cryptography based minimum (k, n)-connected graph

Recently, Lin et al. [29] introduced a (k, n) multi-factor cheating prevention visual cryptographic scheme (MCPVCS) by hiding verification images into shadow images. Through authenticating the verification image and the reconstructed image simultaneously, Lin et al.’s MCPVCS can prevent cheating attack that dishonest participants may collude and cheat the honest one to get a wrong secret image. However, the large n reduces the size of verification image and makes the verification difficult. In this paper, a (k, n)-MCPVCS with the large size of verification image is proposed. There are three main contributions for the proposed (k, n)-MCPVCS: (i) the verification condition in (k, n)-MCPVCS is redefined, (ii) a new minimum (k, n)-connected graph problem is introduced, on which the minimum number of verification images is determined, and (iii) the proposed (k, n)-MCPVCS with the large size of verification image can more easily authenticate the unambiguity of verification image.

Integrating wireless sensing and decision support technologies for real-time farmland monitoring and support for effective decision making

This paper presents the design of a (i) soil sensing and monitoring wireless sensor network (S2M-WSN) that can sense and monitor farmland with distributed and networked motes equipped with multiple soil sensors and (ii) a prototype decision support system (DSS) that analyses the soil data received from S2M-WSN using statistical methods, stored rules and knowledge base (KB) and auto-transmits alerts on the mobile phones of end-users. Both S2M-WSN and the DSS are integrated through (iii) predefined data frame format and interface protocol. The developed system has been deployed both in the laboratory and real crop conditions for verification, validation and performance evaluation. The system is evaluated by considering various performance metrics such as ambiguities associated with data, data packet delivery rates, support delivery performance ratio, system response time, and resultant plant growth. The developed system empowers the end users with assistance in on-field decision making through relevant advisories and alerts at right time on their mobile phones. The authors believe that the developed system would definitely bridge the information gap between end-users and domain experts for sustainable growth of agriculture.

Symbolic reasoning for automatic signal placement

Explicit signaling between threads is a perennial cause of bugs in concurrent programs. While there are several run-time techniques to automatically notify threads upon the availability of some shared resource, such techniques are not widely-adopted due to their run-time overhead. This paper proposes a new solution based on static analysis for automatically generating a performant explicit-signal program from its corresponding implicit-signal implementation. The key idea is to generate verification conditions that allow us to minimize the number of required signals and unnecessary context switches, while guaranteeing semantic equivalence between the source and target programs. We have implemented our method in a tool called Expresso and evaluate it on challenging benchmarks from prior papers and open-source software. Expresso-generated code significantly outperforms past automatic signaling mechanisms (avg. 1.56x speedup) and closely matches the performance of hand-optimized explicit-signal code.

A data-driven CHC solver

We present a data-driven technique to solve Constrained Horn Clauses (CHCs) that encode verification conditions of programs containing unconstrained loops and recursions. Our CHC solver neither constrains the search space from which a predicate's components are inferred (e.g., by constraining the number of variables or the values of coefficients used to specify an invariant), nor fixes the shape of the predicate itself (e.g., by bounding the number and kind of logical connectives). Instead, our approach is based on a novel machine learning-inspired tool chain that synthesizes CHC solutions in terms of arbitrary Boolean combinations of unrestricted atomic predicates. A CEGAR-based verification loop inside the solver progressively samples representative positive and negative data from recursive CHCs, which is fed to the machine learning tool chain. Our solver is implemented as an LLVM pass in the SeaHorn verification framework and has been used to successfully verify a large number of nontrivial and challenging C programs from the literature and well-known benchmark suites (e.g., SV-COMP).

Wave Trajectory Study on the Coast of Lhoknga, Aceh Besar, Indonesia: A Numerical Model Approach

A numerical model of wave trajectory using shoaling and refraction formula was proposed in the coastal waters of Lhoknga, Aceh Besar, Indonesia. The developed model used a two dimensional (2D) numerical methods for wave trajectory with the input of wave height and period; 0.62 m and 8 second for high tide and 0.47 m and 6 second for low tide. This model was tested on site during low tide and high tide conditions for verification. The purpose of this numerical study is to trace the distribution of wave trajectory because of shoaling, wave breaking, and wave refraction. The model determines the wave height and crest pattern of the ray wave trajectory. The simulation result shows the pattern of the wave propagation at Lhoknga beach moves from the northwest to the east and south of the coast. The model also informs that the maximum wave height during high tide condition is 1.72 m and 1.31 m during low tide condition. The result indicates that the coast of Lhoknga has moderate wave conditions caused by a gentle beach bathymetry slope.