Fault‐driven stress testing of distributed real‐time software based on UML models

In a previous article, a stress testing methodology was reported to detect network traffic‐related Real‐Time (RT) faults in distributed RT systems based on the design UML model of a System Under Test (SUT). The stress methodology, referred to as Test LOcation‐driven Stress Testing (TLOST), aimed at increasing the chances of RT failures (violations in RT constraints) associated with a given stress test location (an network or a node under test). As demonstrated and experimented in this article, although TLOST is useful in stress testing different test locations (nodes and network, it does not guarantee to target (test) all RT constraints in an SUT. This is because the durations of message sequences bounded by some RT constraints might never be exercised (covered) by TLOST. A complementary stress test methodology is proposed in this article, which guarantees to target (cover) all RT constraints in an SUT and detect their potential RT faults (if any). Using a case study, this article shows that the new complementary methodology is capable of targeting the RT faults not detected by the previous test methodology. Copyright © 2009 John Wiley & Sons, Ltd.     

A UML-based quantitative framework for early prediction of resource usage and load in distributed real-time systems

This paper presents a quantitative framework for early prediction of resource usage and load in distributed real-time systems (DRTS). The prediction is based on an analysis of UML 2.0 sequence diagrams, augmented with timing information, to extract timed-control flow information. It is aimed at improving the early predictability of a DRTS by offering a systematic approach to predict, at the design phase, system behavior in each time instant during its execution. Since behavioral models such as sequence diagrams are available in early design phases of the software life cycle, the framework enables resource analysis at a stage when design decisions are still easy to change. Though we provide a general framework, we use network traffic as an example resource type to illustrate how the approach is applied. We also indicate how usage and load analysis of other types of resources (e.g., CPU and memory) can be performed in a similar fashion. A case study illustrates the feasibility of the approach.

Communications-oriented development of component-based vehicular distributed real-time embedded systems

We propose a novel model- and component-based technique to support communications-oriented development of software for vehicular distributed real-time embedded systems. The proposed technique supports modeling of legacy nodes and communication protocols by encapsulating and abstracting the internal implementation details and protocols. It also allows modeling and performing timing analysis of the applications that contain network traffic originating from outside of the system such as vehicle-to-vehicle, vehicle-to-infrastructure, and cloud-based applications. Furthermore, we present a method to extract end-to-end timing models to support end-to-end timing analysis. We also discuss and solve the issues involved during the extraction of these models. As a proof of concept, we implement our technique in the Rubus Component Model which is used for the development of software for vehicular embedded systems by several international companies. We also conduct an application-case study to validate our approach.     

Experience and challenges with UML-driven performance engineering of a Distributed Real-Time System

ContextPerformance-related failures of Distributed and Real-Time Software Systems (DRTS’s) can be very costly, e.g., explosion of a nuclear reactor. We reported in a previous work a stress testing methodology to detect performance-related Real-Time (RT) faults in DRTS’s based on the design UML model of a System Under Test (SUT). The stress methodology aimed at increasing the chances of RT failures (violations in RT constraints).ObjectiveAfter stress testing a SUT and finding RT faults, an important immediate question is how to fix (debug) those RT faults and prevent the same RT violations in the future and after deployment. If appropriate solutions to this challenge cannot be found, stress testing and its findings (detection of RT faults) will be of no or little use to the quality assurance goals of the development team.MethodTo move towards systematically solving performance-related problems causing RT faults, we develop a customized version of the standard Software Performance Engineering process and conduct an experiment on a DRTS. The process is iteratively applied to a SUT, while results from stress testing reveal that there are still scenarios in which RT constraints are violated.ResultsApplication of the performance engineering paradigm in this context on a real DRTS enables systematic analysis of performance-related defects and their fixations.ConclusionThe contributions of this work are an initial approach to software performance engineering based on stress testing, and an analysis, based on experimentation, of the open issues that need to be addressed in order to improve the approach.     

Modeling distributed real-time systems with MAST 2

Switched networks have an increasingly important role in real-time communications. The IEEE Ethernet standards have defined prioritized traffic (802.1p) and other QoS mechanisms (802.1q). The Avionics Full-Duplex Switched Ethernet (AFDX) standard defines a hard real-time network based on switched Ethernet. Clock synchronization is also an important service in some real-time distributed systems because it allows a global notion of time for event timing and timing requirements. In the process of defining the new MAST 2 model, clock synchronization modeling capabilities have been added, and the network elements have been enhanced to include switches and routers. This paper introduces the schedulability model that will enable an automatic schedulability analysis of a distributed application using switched networks and clock synchronization mechanisms.     

Scheduler Modeling Based on the Controller Synthesis Paradigm

The controller synthesis paradigm provides a general framework for scheduling real-time applications. Schedulers can be considered as controllers of the applications; they restrict their behavior so that given scheduling requirements are met. We study a modeling methodology based on the controller synthesis paradigm. The methodology allows to get a correctly scheduled system from timed models of its processes in an incremental manner, by application of composability results which simplify schedulability analysis. It consists in restricting successively the system to be scheduled by application of constraints defined from scheduling requirements. The latter are a conjunction of schedulability requirements that express timing properties of the processes and policy requirements about resource management. The presented methodology allows a unified view of scheduling theory and approaches based on timing analysis of models of real-time applications.     

TFSP：一种分布式实时系统的形式化描述工具

Distributed Real Time Systems (DRTS) have very broad applications in space navigation, nuclear reaction,military affairs and industry department where the security and reliability requirement of the DRTS is very high.Thus, how to develop correct DRTS application systems is of vital importance. In this paper, first a formalized nota-tion system -Timed Finite State Processes (TFSP) is proposed to describe the complex dynamic behaviors of DRTS,then we describe a distributed real-time medirAl treatment system by Darwin Architecture language and TFSP.     

城市道多路口交通信号实时控制仿真设计

在单路口交通灯实时控制的基础上对城市道路多路口交通灯实时控制进行了研究。提出了一种双层次子区域的智能划分方法并应用于区域交通信号的实时控制,在子区域基础上建立多交叉口数学模型;运用指数平滑预测模型为BP神经网络模型提供学习所需数据,并将得到的混沌交通流序列与改进泊松函数得到的泊松分布断面发车随机数进行比较。通过上述模型及算法最终得到区域交通路口实时配时方案。     

DOPS——分布式面向对象编程系统

ＤＯＰＳ是我们在Ｓｕｎ工作站网络中设计实现的分布式面向对象编程系统。目前包括并发面向对象编程语言ＣＣ＋＋和该语言在松散耦合分布式环境中的运行支撑系统ＤＲＴＳ。本文分别介绍ＣＣ＋＋和ＤＲＴＳ的设计与实现，最后给出检测结果。     

Rate-monotonic analysis for real-time industrial computing

Issues of real-time resource management are pervasive throughout industrial computing. The underlying physical processes of many industrial computing applications impose explicit timing requirements on the tasks processed by the computer system. These timing requirements are an integral part of the correctness and safety of a real-time system. It is tempting to think that speed (for example, processor speeds or higher communication bandwidths) is the sole ingredient in meeting system timing requirements, but speed alone is not enough. Proper resource-management techniques also must be used to prevent, for example, situations in which long, low priority tasks block higher priority tasks with short deadlines. One guiding principle in real-time system resource management is predictability, the ability to determine for a given set of tasks whether the system will be able to meet all of the timing requirements of those tasks. Predictability calls for the development of scheduling models and analytic techniques to determine whether or not a real-time system can meet its timing requirements. The author illustrates an analysis methodology, rate monotonic analysis, for managing real-time requirements in a distributed industrial computing situation. The illustration is based on a comprehensive robotics example drawn from a typical industrial application