基于UML模型和OCL约束的类间交互测试用例生成方法研究

 面向对象所具有的类、封装、继承、动态连接等特性,使得面向对象测试步骤的划分以及测试策略的选择有别于传统的测试思想.本文针对面向对象软件的特点,采用基于模型的软件测试方法,对UML(United Model Language)设计模型中的顺序图添加OCL(Object Constraints Language)约束,做类间交互的软件测试.本文提出执行图EG生成算法,将顺序图SD转换为执行图EG,解决UML2.0顺序图新增特性中的alt、loop、opt、break四种常见组合片段及其嵌套和多态性问题;为得到最小完备的测试路径,本文提出了EG的遍历策略和测试路径生成算法;最后,根据测试路径确定测试场景,并删除无效场景,生成测试用例.经实验验证,此方法可以基于UML顺序图与OCL约束进行系统地测试.     

Temperature dependence of the threshold current density of aquantum dot laser

Detailed theoretical analysis of the temperature dependence of threshold current density of a semiconductor quantum dot (QD) laser is given. Temperature dependences of the threshold current density components associated with the radiative recombination in QDs and in the optical confinement layer (OCL) are calculated. Violation of the charge neutrality in QDs is shown to give rise to the slight temperature dependence of the current density component associated with the recombination in QD's. The temperature is calculated (as a function of the parameters of the structure) at which the components of threshold current density become equal to each other. Temperature dependences of the optimum surface density of QD's and the optimum thickness of the OCL, minimizing the threshold current density, are obtained. The characteristic temperature of QD laser T_o is calculated for the first time considering carrier recombination in the OCL (barrier regions) and violation of the charge neutrality in QDs. The inclusion of violation of the charge neutrality is shown to be critical for the correct calculation of T_o. The characteristic temperature is shown to fall off profoundly with increasing temperature. A drastic decrease in T_o is shown to occur in passing from temperature conditions wherein the threshold current density is controlled by radiative recombination in QD's to temperature conditions wherein the threshold current density is controlled by radiative recombination in the OCL. The dependences of T_o on the root mean square of relative QD size fluctuations, total losses, and surface density of QDs are obtained     

Testing for Function and Performance: Towards an Integrated Processor Validation Methodology

Microprocessor design teams use a combination of simulation-based and formal verification techniques to validate the pre-silicon models prior to tape-out and chip fabrication. Pseudo-random test case generation to cover the architectural space is still relied upon as the principal means to identify design bugs. However, such methods are limited to functional bugs only. Detection and diagnosis of timing (performance) bugs at the architectural level is largely an expert job. Architects guide the performance team to run manually generated test cases to validate the design from a performance viewpoint. In this paper, we will review some of the new approaches being tried out to automate the generation of performance test cases. We will show how this can be done within the basic framework of current functional validation and testing of pre-silicon processor models. Three categories of reference specifications are used in determining the defect-free pipeline timing behavior associated with generated test cases: (a) axiomatic specifications of intrinsic machine latencies and bandwidths; (b) proven analytical models for simple basic block and loop test cases; and, (c) a stable reference behavioral/functional (pre-RTL) model of the processor under development. We report experimental results obtained in performance validation studies applied to real PowerPC processor development projects.     

The Effect of Coupling on Understanding and Modifying OCL Expressions: An Experimental Analysis

Not all the model constraints can be defined using only UML graphical features due to the limited expressiveness of diagram-based UML notation. To solve this problem, the OCL language was defined as a textual add-on to the UML diagrams, allowing the specification of a wide range of constraints of objects. Aware of the lack of metrics to capture the quality aspects of UML/OCL models and the importance of models in recent initiatives of model-Driven software engineering (such as Model-Driven Development and Model-Driven Architecture), we define a set of metrics for measuring the structural properties of OCL constraints in UML/OCL models. Many of these metrics are defined in terms of navigations, a core concept of OCL that defines coupling between objects. This paper carefully describes a family of experiments we have conducted to ascertain whether any relationship exists between object coupling (defined through metrics related to navigations and collection operations) and two maintainability subcharacteristics: understandability and modifiability of OCL expressions. Empirical evidence that such a relationship exists is shown in the obtained results, however they must be considered as preliminaries results. Further validation is needed to strengthen the conclusions and external validity.     

The limit of sum of Markov Bernoulli variables in systemreliability evaluation

For 2-state maintainable and repairable systems modeled by nonstationary Markov chains, a limiting compound Poisson distribution is derived for the sum of Markov Bernoulli random variables. The result is useful for estimating the distribution of the sum of negative-margin hours in a boundary-crossing scenario involving any physical system with interarrival times of system failures that are negative-exponentially distributed, where the positive- and negative-margin states denote desirable and undesirable operating conditions. three test cases from the IEE Reliability Test system are analyzed. The mean and variance/mean ratio are generated for each case. The results of compound Poisson distribution estimation for the sum of Markov Bernoulli random variables with varying probabilities can be used to solve the problem of estimating the distribution of the popular reliability index (cumulated loss-of-load hours) in large electric power generation systems where the hourly load demand varies     

Integrated system interoperability testing with applications to VoIP

This work has been motivated by the need to test interoperability of systems carrying voice calls over the IP network. The voice over IP (VoIP) systems must be integrated and interoperate with the existing public switched telephone network (PSTN) before they are widely adopted. Standards have been developed to address this problem, but unfortunately different standards bodies and commercial consortiums have defined different standards. Furthermore, the prevailing VoIP standard such as H.323 is incomplete, complex, and presents the implementers with "vendors latitudes". As a result, there is no guarantee that the integrated VoIP systems would interoperate properly even if the implementations are all H.323-compliant. Thus interoperability testing has become indispensable. We want to test all the system interoperations by exercising all the required patterns of "interoperating behaviors". On the other hand, test execution in real environment is expensive, and we want to minimize the number of tests while maintaining the coverage. We present a general method for automatic generation of test cases, which cover all the required system interoperations and contain a minimal number of tests. We study data structures and efficient test generation algorithms, which take time proportional to the total test case size. Finally, we report experimental results on VoIP systems.     

Design of signals for analog communication

A method for the design of time-limited and effectively band-limited waveforms for analog communication systems is developed. The design problem is first formulated in theL_2 (0, T)space. Nonlinear modulation threshold effects are incorporated directly into the design by introducing constraints in the form of minimum distance between points on the locus. It is shown that all pertinent information can be expressed in terms of the inner product function generated by the locus and its cross derivative. The design is then transformed into a constrained minimization problem in a space of inner product functions. The cases of stationary locus andN-dimensional locus are further investigated.     

Iterative Antirandom Testing

Antirandom testing is a variation of pure random testing, which is the process of generating random patterns and applying it to a system under test (both software systems and hardware systems). However, research studies have shown that pure random testing is relatively less effective at fault detection than other testing techniques. Antirandom testing improves the fault-detection capability of random testing by employing the location information of previously executed test cases. In antirandom testing we select test case such that it is as different as possible from all the previous executed test cases. Unfortunately, this method essentially requires enumeration of the input space and computation of each input pattern when used on an arbitrary set of existing test data. This avoids scale-up to large test sets and (or) long input vectors. The objective of this paper is to find a more efficient method of the test generation which does not need any computation. The key idea of proposed approach is an iterative application of the short antirandom tests where the first test vector in each iteration is generated randomly. Moreover, we propose a new metric the Maximal Minimal Hamming Distance (MMHD) which allows us to define an optimal antirandom test with restricted number of patterns. Experimental results are given to evaluate the performance of the new approach.     

Simulation Analysis on Conducted EMD Caused by Valves in $pm$ 800 kV UHVDC Converter Station

Wideband frequency electromagnetic (EM) noise generated during the turn- on and turn-off processes of thyristor valves in converter stations is conducted along the primary circuitry, and may interfere with secondary systems. The EM interference (EMI) problem in a $pm$800 kV ultra-HVdc converter station is an important issue that should be studied carefully in the design stage. A method to analyze the conducted EM disturbance (EMD) based on time-domain wideband circuit simulation is proposed here, which is verified through the field test results of a $pm$500 kV converter station. Models of major equipment are described. The EMD levels of a $pm$800 kV converter station, which is currently being planned and built in China, are calculated, and compared with those of a $pm$500 kV converter station.      

Every discrete 2D autonomous system admits a finite union of parallel lines as a characteristic set

In this paper, we show that every discrete 2D autonomous system, that is described by a set of linear partial difference equations with constant real coefficients, admits a finite union of parallel lines as a characteristic set. In order to prove our claim, we first look at a special class of scalar discrete 2D systems and provide such characteristic sets for systems in this class. This special class has the property that systems in this class have their quotient rings to be finitely generated modules over a one-variable Laurent polynomial subring of the original two-variable Laurent polynomial ring in the shift operators. We show that such systems always admit a finite collection of horizontal lines for a characteristic set. We then extend this result to non-scalar discrete 2D autonomous systems. We achieve this in two steps: first, we show that every scalar discrete 2D system can be converted into a system in the above-mentioned class by a coordinate transformation on the independent variables set, \(\mathbb {Z}^2\). Using this we then show that characteristic sets for the original system can be found by applying the inverse coordinate transformation on characteristic sets of the transformed system. Since the transformed system, by virtue of being in the special class, admits a finite union of horizontal lines as a characteristic set, the original system is guaranteed to admit a characteristic set that is a coordinate transformation applied to a finite union of horizontal lines. The coordinate transformation maps this union of horizontal lines to a union of parallel, but possibly tilted, lines. In the next step, we generalize the scalar case to the general vector case: that is, systems with more than one dependent variables. The main motivation for studying characteristic sets that are unions of finitely many parallel lines is that, arguably, such sets can be called “thin” in \(\mathbb {Z}^2\) in comparison to the prevalent notions of convex cones and half-spaces as characteristic sets (see “Appendix 1”).     

Scheduling of frequently communicating tasks

Gang scheduling is an efficient resource management scheme for distributed systems which combines elements of time sharing and space sharing. It is a suitable technique particularly in the case when parallel tasks have to be running concurrently to make progress in communication. This paper studies the impact on scheduling performance when dynamically generated sequential gangs exist in the workload. In the case of sequential gangs, a subsequent gang can be dynamically generated after the execution of the initial gang based on affinity information which resides on the caches of the previously seized processors. The performance of different gang‐scheduling algorithms is examined for various cases of workload compositions which range from cases with a low demand for dynamically generated gangs to cases with a high ratio of sequential gangs to solitary gangs. A simulation model is implemented to address associated performance issues. Copyright © 2011 John Wiley & Sons, Ltd.     

Chaos generation in fractional-order switched systems and its digital implementation

A double-scroll chaotic attractor generated by a fractional-order switched system is presented. Based on unstable dissipative systems (UDS) and a switching law, a fractional-order UDS is proposed. Chaos behavior is found with a fractional order as low as 2.568 by satisfying the stability criterion for fractional order chaotic systems. The fractional-order switched system is transformed to an equivalent switched system with augmented states. Then, the equivalent system is straightforward implemented on an ARM system-on-chip board by using Python high level programming language. Numerical simulations are in good agreement with experimental results, which demonstrates the usefulness of proposed method. Additionally, the test 0–1 and a chaos definition for finite state sets are given to demonstrate chaotic behavior. Finally, a random number generator is also proposed as a possible application.     

A Novel Adaptive Design Methodology for Minimum Leakage Power Considering PVT Variations on Nanoscale VLSI Systems

This paper proposes a novel design method to minimize the leakage power during standby mode using a novel adaptive supply voltage and body-bias voltage generating technique for nanoscale VLSI systems. The process, voltage, and temperature (PVT) variations are monitored and controlled independently by their own dedicated systems. The minimum level of $V_{rm DD}$ and the optimum body-bias voltage are generated for different temperature and process conditions adaptively using a lookup table method based on the PVT monitoring and controlling systems. The power supply variations is accurately compensated adaptively through the monitoring circuits based on the propagation delay change of the inverter chains. The subthreshold current as well as gate-tunneling and band-to-band-tunneling currents are monitored and minimized adaptively by the optimally generated body-bias voltage. The proposed design method reduces the leakage power at least by 500 times for ISCAS'85 benchmark circuits designed using 32-nm CMOS technology comparing to the case where the method is not applied.      

Multiuser detection for overloaded CDMA systems

Multiuser detection for overloaded code-division multiple-access (CDMA) systems, in which the number of users is larger than the dimension of the signal space, is of particular interest when bandwidth is at a premium. In this paper, certain fundamental questions are answered regarding the asymptotic forms and performance of suboptimum multiuser detectors for cases where the desired and/or interfering signal subspaces are of reduced rank and/or have a nontrivial intersection. In the process, two new suboptimum detectors are proposed that are especially well suited to overloaded systems, namely, the group pseudo-decorrelator and the group minimum mean-squared error (MMSE) detector. The former is seen to be the correct extension of the group decorrelator in the sense that it is the limiting form (in the low-noise regime) of the group MMSE detector. Pseudo-decorrelation is also used as a feedforward filter in a new decision feedback scheme. For the particular case of real-valued modulation, it is shown that the proposals of the so-called "improved" linear (also known as "linear-conjugate" or "widely linear") detectors were more simply derived earlier using the idea of minimal sufficiency, which we also apply to the new detectors of this paper.     

Modeling and Interoperability Test Case Generation of a Real-Time QoS Monitoring Protocol

QoS monitoring is a kind of real-time systems which allows each level of the system to track the ongoing QoS levels achieved by the lower network layers. For these systems, real-time communication between corresponding transport protocol objects is essential for their correct behavior. When two or more entities are employed to perform a certain task as in the case of communication protocols, the capability to do so is called interoperability and considered as the essential aspect of correctness of communication systems. This paper describes a formal approach on modeling and interoperability test case generation of a real-time QoS monitoring protocol. For this, we specify the behavior of flow monitoring of transport layer QoS protocol, i.e., METS protocol, which is proposed to address QoS from an end-to-end's point of view, based on QoS architecture model which includes ATM network in lower layers. We use a real-time Input/Output Finite State Machine to model the behavior of real-time flow monitoring over time. From the modeled real-time I/OFSM, we generate interoperability test cases to check the correctness of METS protocol's flow monitoring behaviors for two end systems. A new approach to efficient interoperability testing is described and the method of interoperability test cases generation is shown with the example of METS protocol's flow monitoring. The current TTCN is not appropriate for testing real-time and multimedia systems. Because test events in TTCN are for message-based system and not for stream-based systems, the real-time in TTCN can only be approximated. This paper also proposes the notation of real-time Abstract Test Suite by means of real-time extension of TTCN. This approach gives the advantages that only a few syntactical changes are necessary, and TTCN and real-time TTCN are compatible. This formal approach on interoperability testing can be applied to the real-time protocols related to IMT-2000, B-ISDN and real-time systems.     

LAN Protocol Validation and Evaluation

We are using simulation to validate and evaluate the performance of the proposed IEEE 802.4 Token-Passing Bus Medium Access Control (MAC) Protocol for local area networks. We will use our discussion of this modeling study to present our technique for protocol validation. We will also present some of our validation and performance results. Our modeling technique is unusual in two important respects. First, it transforms the formal specification of the protocol by a direct and simple technique into a simulation program. Second, testable assertions about the protocors expected behavior, under both normal and abnormal conditions, are easily transformed into simulation test cases. Our protocol validation technique runs test cases on the simulation model. These test cases are based upon "behavioral assertions" which were derived from the design objectives and expected use of the protocol. Our validation results are discussed in terms of the behavioral assertions tested and the success or failure of meeting these assertions. We also report on simulation performance predictions for some special test cases.     

Operating Characteristics of Semiconductor Quantum Well Lasers as Functions of the Waveguide Region Thickness

The performance characteristics of semiconductor lasers based on quantum wells (QWs) are theoretically studied as functions of the thickness of the waveguide region [optical confinement layer (OCL)]. The maximum modal gain, optical-confinement factor (in QWs, OCLs, and emitters), threshold current density, electron and hole densities (in QWs and OCLs), internal optical loss (in QWs, OCLs, and cladding layers), internal differential quantum efficiency, currents of stimulated and spontaneous recombination and the output optical power of the laser are calculated as functions of the OCL thickness. It is shown that up to pump current densities of 50 kA/cm² the dependence of the output power of the considered lasers on the OCL thickness is weak in the thickness range of 1.5–2.8 μm. This result is important for the development of high-brightness lasers, since such lasers use a wide waveguide to ensure low radiation divergence. It is shown that, at very high pump-current densities, the output power has a maximum as a function of the OCL width.