На пути к автоматической дедуктивной верификации C-программ с Sisal-циклами в системе C-lightVer

The C-lightVer system is developed in IIS SB RAS for C-program deductive verification. C-kernel is an intermediate verification language in this system. Cloud parallel programming system (CPPS) is also developed in IIS SB RAS. Cloud Sisal is an input language of CPPS. The main feature of CPPS is implicit parallel execution based on automatic parallelization of Cloud Sisal loops. Cloud-Sisal-kernel is an intermediate verification language in the CPPS system. Our goal is automatic parallelization of such a superset of C that allows implementing automatic verification. Our solution is such a superset of C-kernel as C-Sisal-kernel. The first result presented in this paper is an extension of C-kernel by Cloud-Sisal-kernel loops. We have obtained the C-Sisal-kernel language. The second result is an extension of C-kernel axiomatic semantics by inference rule for Cloud-Sisal-kernel loops. The paper also presents our approach to the problem of deductive verification automation in the case of finite iterations over data structures. This kind of loops is referred to as definite iterations. Our solution is a composition of symbolic method of verification of definite iterations, verification condition metageneration and mixed axiomatic semantics method. Symbolic method of verification of definite iterations allows defining inference rules for these loops without invariants. Symbolic replacement of definite iterations by recursive functions is the base of this method. Obtained verification conditions with applications of recursive functions correspond to logical base of ACL2 prover. We use ACL2 system based on computable recursive functions. Verification condition metageneration allows simplifying implementation of new inference rules in a verification system. The use of mixed axiomatic semantics results to simpler verification conditions in some cases.В Институте систем информатики СО РАН разрабатывается система C-lightVer для дедуктивной верификации C-программ. C-kernel является промежуточным языком верификации в данной системе. Система облачного параллельного программирования (CPPS) также разрабатывается в Институте систем информатики СО РАН. Cloud Sisal является входным языком системы CPPS. Главной особенностью системы CPPS является неявное параллельное исполнение, основанное на автоматическом распараллеливании циклов Cloud Sisal. Cloud-Sisal-kernel является промежуточным языком верификации в системе CPPS. Нашей целью является автоматическое распараллеливание такого надмножества языка C, которое позволяет реализовать автоматическую верификацию. Нашим решением является такое надмножество языка C-kernel, как язык C-Sisal-kernel. Первым результатом, представленным в данной статье, является расширение языка C-kernel циклами языка Cloud-Sisal-kernel. В результате был разработан язык C-Sisal-kernel. Вторым результатом, представленным в данной статье, является расширение аксиоматической семантики языка C-kernel правилом вывода для циклов языка Cloud-Sisal-kernel. В данной статье также представлен наш подход к проблеме автоматизации дедуктивной верификации в случае финитных итераций над структурами данных. Такие циклы называются финитными итерациями. Нашим решением является композиция символического метода верификации финитных итераций, метагенерации условий корректности и смешанной аксиоматической семантики. Символический метод верификации финитных итераций позволяет задавать правила вывода для таких циклов без инвариантов. Символическая замена финитных итераций рекурсивными функциями является основой данного метода. Полученные условия корректности с применениями рекурсивных функций соответствуют логической основе системы доказательства ACL2. Мы используем систему ACL2, основанную на вычислимых рекурсивных функциях. Метагенерация условий корректности позволяет упростить реализацию новых правил вывода в системе верификации. Использование смешанной аксиоматической семантики приводит в некоторых случаях к более простым условиям корректности

Комплексный подход системы C-lightVer к автоматизированной локализации ошибок в C-программах

The C-lightVer system for the deductive verification of C programs is being developed at the IIS SB RAS. Based on the two-level architecture of the system, the C-light input language is translated into the intermediate C-kernel language. The meta generator of the correctness conditions receives the C-kernel program and Hoare logic for the C-kernel as input. To solve the well-known problem of determining loop invariants, the definite iteration approach was chosen. The body of the definite iteration loop is executed once for each element of the finite dimensional data structure, and the inference rule for them uses the substitution operation rep, which represents the action of the cycle in symbolic form. Also, in our meta generator, the method of semantic markup of correctness conditions has been implemented and expanded. It allows to generate explanations for unproven conditions and simplifies the errors localization. Finally, if the theorem prover fails to determine the truth of the condition, we can focus on proving its falsity. Thus a method of proving the falsity of the correctness conditions in the ACL2 system was developed. The need for more detailed explanations of the correctness conditions containing the replacement operation rep has led to a change of the algorithms for generating the replacement operation, and the generation of explanations for unproven correctness conditions. Modifications of these algorithms are presented in the article. They allow marking rep definition with semantic labels, extracting semantic labels from rep definition and generating description of break execution condition.В ИСИ СО РАН разрабатывается система C-lightVer для дедуктивной верификации С-программ. Исходя из двухуровневой архитектуры системы, входной язык C-light транслируется в промежуточный язык C-kernel. Метагенератор условий корректности принимает на вход C-kernel программу и логику Хоара для C-kernel. Для решения известной проблемы задания инвариантов циклов выбран подход финитных итераций. Тело цикла финитной итерации исполняется один раз для каждого элемента структуры данных конечной размерности, а правило вывода для них использует операцию замены rep, выражающую действие цикла в символической форме. Также в нашем метагенераторе внедрен и расширен метод семантической разметки условий корректности. Он позволяет порождать пояснения для недоказанных условий и упрощает локализацию ошибок. Наконец, если система ACL2 не справляется с установлением истинности условия, можно сосредоточиться на доказательстве его ложности. Ранее нами был разработан способ доказательства ложности условий корректности для системы ACL2. Необходимость в более подробных объяснениях условий корректности, содержащих операцию замены rep, привела к изменению алгоритмов генерации операции замены, извлечения семантических меток и генерации объяснений недоказанных условий корректности. В статье представлены модификации данных алгоритмов. Эти изменения позволяют пометить исходный код функции rep семантическими метками, извлекать семантические метки из определения rep, а также генерировать описание условия исполнения инструкции break

Algebraic Stream Processing

We identify and analyse the typically higher-order approaches to stream processing in the literature. From this analysis we motivate an alternative approach to the specification of SPSs as STs based on an essentially first-order equational representation. This technique is called Cartesian form specification. More specifically, while STs are properly second-order objects we show that using Cartesian forms, the second-order models needed to formalise STs are so weak that we may use and develop well-understood first-order methods from computability theory and mathematical logic to reason about their properties. Indeed, we show that by specifying STs equationally in Cartesian form as primitive recursive functions we have the basis of a new, general purpose and mathematically sound theory of stream processing that emphasises the formal specification and formal verification of STs. The main topics that we address in the development of this theory are as follows. We present a theoretically well-founded general purpose stream processing language ASTRAL (Algebraic Stream TRAnsformer Language) that supports the use of modular specification techniques for full second-order STs. We show how ASTRAL specifications can be given a Cartesian form semantics using the language PREQ that is an equational characterisation of the primitive recursive functions. In more detail, we show that by compiling ASTRAL specifications into an equivalent Cartesian form in PREQ we can use first-order equational logic with induction as a logical calculus to reason about STs. In particular, using this calculus we identify a syntactic class of correctness statements for which the verification of ASTRAL programmes is decidable relative to this calculus. We define an effective algorithm based on term re-writing techniques to implement this calculus and hence to automatically verify a very broad class of STs including conventional hardware devices. Finally, we analyse the properties of this abstract algorithm as a proof assistant and discuss various techniques that have been adopted to develop software tools based on this algorithm

Fiber-Reinforced Plastics

This book deepens the study and knowledge on fiber-reinforced plastics (FRPs), which are composite materials made of a polymer matrix reinforced with fibers. The fibers are usually glass, carbon, or aramid, although other fibers such as paper, wood, or asbestos are sometimes used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, and phenol-formaldehyde resins are still in use. Among, the most prominent applications of FRPs are in the aerospace, automotive, marine, and construction industries. The development of FRPs has a very promising future with a marked annual increase and with a wide range of sources. This book presents comprehensive information on FRPs and their wide variety of applications in the industry worldwide

Use of proofs-as-programs to build an anology-based functional program editor

This thesis presents a novel application of the technique known as proofs-as-programs. Proofs-as-programs defines a correspondence between proofs in a constructive logic and functional programs. By using this correspondence, a functional program may be represented directly as the proof of a specification and so the program may be analysed within this proof framework. CʸNTHIA is a program editor for the functional language ML which uses proofs-as-programs to analyse users' programs as they are written. So that the user requires no knowledge of proof theory, the underlying proof representation is completely hidden. The proof framework allows programs written in CʸNTHIA to be checked to be syntactically correct, well-typed, well-defined and terminating. CʸNTHIA also embodies the idea of programming by analogy — rather than starting from scratch, users always begin with an existing function definition. They then apply a sequence of high-level editing commands which transform this starting definition into the one required. These commands preserve correctness and also increase programming efficiency by automating commonly occurring steps. The design and implementation of CʸNTHIA is described and its role as a novice programming environment is investigated. Use by experts is possible but only a sub-set of ML is currently supported. Two major trials of CʸNTHIA have shown that CʸNTHIA is well-suited as a teaching tool. Users of CʸNTHIA make fewer programming errors and the feedback facilities of CʸNTHIA mean that it is easier to track down the source of errors when they do occur

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 407)

This bibliography lists 289 reports, articles and other documents announced in the NASA Scientific and Technical Information System during Nov. 1995. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

First Annual Workshop on Space Operations Automation and Robotics (SOAR 87)

Several topics relative to automation and robotics technology are discussed. Automation of checkout, ground support, and logistics; automated software development; man-machine interfaces; neural networks; systems engineering and distributed/parallel processing architectures; and artificial intelligence/expert systems are among the topics covered