TESTING OF MICROPROCESSORS

With the growing use of the microprocessors the problematics of testing become more and more important for the reliability of the instrumentation. The paper gives a survey of the usual strategies and methods for CPU testing in microprocessor controlled equipment. The effects of the state-of-the-art field service methods on the self-test technology are discussed. Description of a new algorithm based on information compression is given together with some related realization experiences

Optimal trajectory generation for Petri nets

Recently, the increasing complexity of IT systems requires the early verification and validation of the system design in order to avoid the costly redesign. Furthermore, the efficiency of system operation can be improved by solving system optimization problems (like resource allocation and scheduling problems). Such combined optimization and validation, verification problems can be typically expressed as reachability problems with quantitative or qualitative measurements. The current paper proposes a solution to compute the optimal trajectories for Petri net-based reachability problems with cost parameters. This is an improved variant of the basic integrated verification and optimization method introduced in [11] combining the efficiency of Process Network Synthesis optimization algorithms with the modeling power of Petri nets

Semantic Data Management in IT Service Performance Assurance

In today's dynamic and highly composed environments, IT service performance and dependability assurance require efficient reasoning about the performance and dependability effects of faults and the countermeasures to choose, using limited knowledge. Model- and observation-based qualitative error propagation analysis methods can be applied to this end; however, providing support for the human, as well as conceptually structured machine interpretation of sets of competing error propagation hypotheses is an open problem. This paper proposes the application of Formal Concept Analysis (FCA) for these tasks. A natural way to represent error propagation hypothesis sets as formal contexts is proposed, and the visual diagnostic exploration of formal context lattices is introduced. On this basis, potential applications of FCA in performance and dependability assurance activities are characterized

UML ACTION SEMANTICS FOR MODEL TRANSFORMATION SYSTEMS

The Action Semantics for UML provides a standard and platform independent way to describe the behavior of methods and executable actions in object-oriented system design prior to implementation allowing the development of highly automated and optimized code generators for UML CASE tools. Model transformation systems provide visual but formal background to specify arbitrary transformations in the Model Driven Architecture (the leading trend in software engineering). In the current paper, we describe a general encoding of model transformation systems as executable Action Semantics expressions to provide a standard way for automatically generating the implementation of formal (and provenly correct) transformations by off-the-shelf MDA tools. In addition, we point out a weakness in the Action Semantics standard that must be improved to achieve a stand-alone and functionally complete action specification language

CONTROL FLOW CHECKING IN MULTITASKING SYSTEMS

The control flow checking technique presented in our paper is based on the new watchdog- processor method SEIS1 (Signature Encoded Instruction Stream). This method is in- tended to check the still uncovered area of state-of-the-art microprocessors using on-chip caches or instruction pipelines, since the processor instruction bus needs not be monitored. The control flow is checked using assigned actual signatures and embedded reference sig- natures. Since the actual and reference signatures are embedded in the checked program, the usual reference database and the time-consuming search/ compare engine in the watch- dog can be omitted. The evaluation of the actual signature is a simple combinatorial task allowing high speed and thus the sharing of the watchdog between different tasks and processors. The checking method has been extended to higher levels of the application like simultaneous check of different processes and their synchronization in multitasking systems

Extreme Value Analysis for Time-variable Mixed Workload

Proper timeliness is vital for a lot of real-world computing systems. Understanding the phenomena of extreme workloads is essential because unhandled, extreme workloads could cause violation of timeliness requirements, service degradation, and even downtime. Extremity can have multiple roots: (1) service requests can naturally produce extreme workloads; (2) bursts could randomly occur on a probabilistic basis in case of a mixed workload in multiservice systems; (3) workload spikes typically happen in deadline bound tasks.Extreme Value Analysis (EVA) is a statistical method for modeling the extremely deviant values corresponding to the largest values. The foundation mathematics of EVA, the Extreme Value Theorem, requires the dataset to be independent and identically distributed. However, this is not generally true in practice because, usually, real-life processes are a mixture of sources with identifiable patterns. For example, seasonality and periodic fluctuations are regularly occurring patterns. Deadlines can be purely periodic, e.g., monthly tax submissions, or time variable, e.g., university homework submission with variable semester time schedules.We propose to preprocess the data using time series decomposition to separate the stochastic process causing extreme values. Moreover, we focus on the case where the root cause of the extreme values is the same mechanism: a deadline. We exploit known deadlines using dynamic time warp to search for the recurring similar workload peak patterns varying in time and amplitude

Designing the automatic transformation of visual languages

AbstractThe design process of complex systems requires a precise checking of the functional and dependability attributes of the target design. The growing complexity of systems necessitates the use of formal methods, as the exhaustiveness of checks performed by the traditional simulation and testing is insufficient.For this reason, the mathematical models of various formal verification tools are automatically derived from UML-diagrams of the model by mathematical transformations guaranteeing a complete consistency between the target design and the models of verification and validation tools.In the current paper, a general framework for an automated model transformation system is presented. The method starts from a uniform visual description and a formal proof concept of the particular transformations by integrating the powerful computational paradigm of graph transformation, planner algorithms of artificial intelligence, and various concepts of computer engineering

An Optimization Based Design for Integrated Dependable Real-Time Embedded Systems

Moving from the traditional federated design paradigm, integration of mixedcriticality software components onto common computing platforms is increasingly being adopted by automotive, avionics and the control industry. This method faces new challenges such as the integration of varied functionalities (dependability, responsiveness, power consumption, etc.) under platform resource constraints and the prevention of error propagation. Based on model driven architecture and platform based design’s principles, we present a systematic mapping process for such integration adhering a transformation based design methodology. Our aim is to convert/transform initial platform independent application specifications into post integration platform specific models. In this paper, a heuristic based resource allocation approach is depicted for the consolidated mapping of safety critical and non-safety critical applications onto a common computing platform meeting particularly dependability/fault-tolerance and real-time requirements. We develop a supporting tool suite for the proposed framework, where VIATRA (VIsual Automated model TRAnsformations) is used as a transformation tool at different design steps. We validate the process and provide experimental results to show the effectiveness, performance and robustness of the approach

Önellenőrzés és futásidejű verifikáció számítógépes programokban = Self-checking and run-time verification in computer programs

A kutatás eredménye egy olyan, futásidejű hibadetektálásra alkalmas módszerkészlet kidolgozása számítógépes programokhoz, amely formálisan megalapozott és illeszkedik a modell alapú tervezési folyamathoz. A futásidejű verifikáció matematikai alapja egy általunk definiált, UML állapottérképekhez illesztett temporális logikai nyelv (SC-LTL) valamint az ehhez kidolgozott gyors és kis erőforrásigényű ellenőrzési algoritmus. Az ellenőrzést megvalósító forráskód részletek (assertions) generálására automatikus kódgenerátort fejlesztettünk. A módszerkészlet alapján a futásidejű verifikáció két szinten végezhető el: (1) A fejlesztés korai fázisaiban (a követelményanalízis után) a tervező a program biztonságos működéséhez tartozó követelményeket formalizálja az SC-LTL temporális logika segítségével. Ezeket futásidőben a programba illesztett kódrészletek segítségével ellenőrizzük. Így a későbbi fejlesztési fázisokban előforduló tervezési hibák következményei is kimutathatók. (2) A fejlesztés előrehaladtával rendelkezésre álló részletes viselkedési modell mint referencia alapján történik a program állapot- és akciószekvenciáinak teljes ellenőrzése, a modellből szintén automatikusan generált, futásidejű monitorozást biztosító úgynevezett watchdog kód segítségével. Ennek célja elsősorban az implementációs hibák és a működési hibák (tranziens hardver hibák) felderítése. A hibadetektálás módszerkészletét kiegészítettük a hibakezelés modellezésére és verifikációjára szolgáló eljárásokkal. | The main result of the research is the elaboration of a set of methods that can be applied for the run-time verification of computer programs. These methods are formally proven and fit well to the model based software development process. The mathematical basis of run-time verification is our temporal logic language (SC-LTL) that is based on UML statechart diagrams, and the corresponding fast and low resource-demanding checker algorithm. To derive the assertions (i.e., the program code snippets that implement the checking), we have developed an automatic source code generator. On the basis of this set of methods, run-time checking of program execution is supported at two levels: (1) In the early phases of development the designer can formalize the program safety and liveness requirements using SC-LTL. These requirements are checked in run-time by the automatically generated assertions. This way design errors introduced in later design phases can also be detected. (2) The full checking of the state- and action sequences of program execution is based on a detailed design model constructed in the last development phases. The run-time monitoring is performed by a so-called watchdog code that is generated from the fully elaborated statechart model automatically. This is able to detect both implementation and operational errors. To complete the error detection framework, we proposed a statechart based method for the modeling and verification of run-time exception handling

Operációkutatási módszerek műszaki informatikai rendszerek analízisében és verifikációjában = Operation Research Methods for the Analysis and Verification of Information Technology Systems

Kidolgoztuk a Petri-hálók és produkciós hálók (PNS) egységes szemléletű leírását. Megfogalmaztuk az "optimális trajektória generálásának" problémáját Petri-hálós modellekre. A megoldásként kidolgozott és implementált algoritmus egyúttal temporális logikai követelményeket is vizsgál a modellen. Az algoritmust gyorsítottuk a PNS logikai bázisa fölötti kereséssel. A SPIN modellellenőrzőt magát használva egy másik megoldást is adtunk a problémára, valamint gráftranszformációs rendszerek optimalizálására. Megadtuk a lineáris korlátozási feltételekkel adott szeparábilis konkáv minimalizálási feladat egy elégséges optimalitási kritériumát, mely a Branch-and-Bound típusú algoritmusban használható fel megállási kritériumként. A magasszintű leírásokból a Petri-hálós modellbe történő transzformációkat matematikai alapokon definiáltuk, megvalósításukra automatikus modelltranszformációs megoldást dolgoztunk ki: egy algoritmust, amely GRM profillal adott modellből generálja a Petri-hálót, és egy általános algoritmust, amely UML modellekből származtat a diagnosztika alapjául szolgáló modelleket. Megvizsgáltuk ezen modellek illeszthetőségét a szabványokhoz. Multiprocesszoros rendszerek diagnosztizálására egy PNS technikákat használó algoritmust adtunk, melynek várható hatékonyságát igazoltuk. Munkálatok folytak a diagnosztika tesztalapú megközelítésére, és diagnosztikai modellek kísérletes paraméterezésére. Kísérleteket végeztünk az IBM Holosofx ipari workflow modellező eszköz illesztésére. | A unified treatment for Petri nets and process network (PNS) problems was defined. The 'optimal trajectory generation problem' for Petri nets was defined. Elaboration and implementation of an algorithm that is able not only to give the optimal trajectory but to verify temporal logic requirements for Petri nets. This algorithm was accelerated using Branch-and-Bound method over the logical basis of the feasible process networks. Another algorithm to solve the problem using only the SPIN model checker was elaborated. The optimization of graph transformation systems with time was solved based on the same technique. A sufficient optimality criteria was given for constrained, concave minimization problems. The precise mathematics of the model transformation from high-level models to Petri nets was defined, and automatic model transformations were carried out to realize these transformations: a transformation from UML models given by the GRM profile to Petri nets and a general algorithm that delivers models to diagnose from UML models. The conformancy of these models to standards was investigated. The probabilistic diagnosis problem in multiprocessor systems was solved using PNS techniques. The efficiency of the method was shown. There were efforts to elaborate a test-based approach of diagnostics, and to parameterize diagnostics models based on dependability experiments. Experiments were carried out to transform IBM Holosofx models to Petri nets