MiSFIT: Mining Software Fault Information and Types

As software becomes more important to society, the number, age, and complexity of systems grow. Software organizations require continuous process improvement to maintain the reliability, security, and quality of these software systems. Software organizations can utilize data from manual fault classification to meet their process improvement needs, but organizations lack the expertise or resources to implement them correctly. This dissertation addresses the need for the automation of software fault classification. Validation results show that automated fault classification, as implemented in the MiSFIT tool, can group faults of similar nature. The resulting classifications result in good agreement for common software faults with no manual effort. To evaluate the method and tool, I develop and apply an extended change taxonomy to classify the source code changes that repaired software faults from an open source project. MiSFIT clusters the faults based on the changes. I manually inspect a random sample of faults from each cluster to validate the results. The automatically classified faults are used to analyze the evolution of a software application over seven major releases. The contributions of this dissertation are an extended change taxonomy for software fault analysis, a method to cluster faults by the syntax of the repair, empirical evidence that fault distribution varies according to the purpose of the module, and the identification of project-specific trends from the analysis of the changes

Identification of Crash Fault & Value Fault for Random Network in Dynamic Environment

During the past few years distributed systems have been the focus of considerable research in computer science. Fault tolerance in distributed systems is a wide area with a significant body of literature that is vastly diverse in methodology and terminology. Fault tolerance is the ability of a system to perform its function correctly even in the presence of internal faults. An extensive methodology has been developed in this field over the past few years, and a number of fault-tolerant machines have been developed but most dealing with random hardware faults, while a smaller number deal with software, design and operator faults to varying degrees. Our work mainly focuses on the simulation of the system that deals with software faults means the faults that occur because of the failure or error in the internal software component. Our work is restricted to distributed diagnosis in dynamic fault environment. Basically we have created different not-completely connected random networks with number of nodes ranging from 8 to 256.Then we have induced faults to these networks dynamically using poison distribution. Three different algorithms have been implemented to detect the faults and the comparison among these algorithms, based on delay latency and number of message exchanges, has been represented graphically. The software faults that we had dealt with are crash fault and value fault in a distributed system (not-completely connected network). Although many researches have been done in the crash fault area but very less work has been done in diagnosing the value faults in dynamic fault environment

Research in computer science

Synopses are given for NASA supported work in computer science at the University of Virginia. Some areas of research include: error seeding as a testing method; knowledge representation for engineering design; analysis of faults in a multi-version software experiment; implementation of a parallel programming environment; two computer graphics systems for visualization of pressure distribution and convective density particles; task decomposition for multiple robot arms; vectorized incomplete conjugate gradient; and iterative methods for solving linear equations on the Flex/32

A new fast-acting backup protection strategy for embedded MVDC links in future distribution networks

This paper presents a new fast-acting backup protection strategy for future hybrid ac-dc distribution networks. By examining the impedance measured by a distance protection relay measuring from the “ac-side” of the network, a unique characteristic is established for faults occurring on the “dc-side” of an embedded medium-voltage dc (MVDC) link, interconnecting two 33 kV distribution network sections. Based on the identified impedance characteristic, appropriate settings are developed and deployed on a verified software model of a commercially available distance protection relay. To remain stable for ac-side faults, it is found that the tripping logic of the device must be altered to provide correct time grading between standard, ac, protection zones and the fast-acting dc region, which can identify faults on the dc system within 40 ms. An additional confirmatory check is also employed to reduce the likelihood of mal-operation. Trials on a test system derived from an actual distribution network, which employs distance protection, are shown to provide stable operation for both ac-side and dc-side pole-pole and pole-pole-ground fault

Research in computer science

Several short summaries of the work performed during this reporting period are presented. Topics discussed in this document include: (1) resilient seeded errors via simple techniques; (2) knowledge representation for engineering design; (3) analysis of faults in a multiversion software experiment; (4) implementation of parallel programming environment; (5) symbolic execution of concurrent programs; (6) two computer graphics systems for visualization of pressure distribution and convective density particles; (7) design of a source code management system; (8) vectorizing incomplete conjugate gradient on the Cyber 203/205; (9) extensions of domain testing theory and; (10) performance analyzer for the pisces system

Studi Pemanfaatan Relai Jarak Quadrilateral untuk Proteksi Saluran Distribusi dengan Pembangkit Tersebar

Installation of distributed generations (DGs) in distribution network bring benefits for power system operation. However, DGs change the distribution network topologies from radial with one source into multi-sources network, hence magnitude and direction of the current will also change. Consequently, the existing distribution line protection i.e. current based protection, experience performances deterioration. To overcome this problem, distance relays, which work based on calculated impedance is proposed. However, since mho distance relays fail to detect faults through resistance in previous research, quadrilateral characteristic of distance relay is chosen. Quadrilateral distance relays have separate setting for reach and resistance; hence it is expected it will accommodate fault resistance. Therefore, this research aims to identify the performance of quadrilateral distance relay in protecting distribution lines that having DG. The research method is computer simulation where quadrilateral distance relays performance is tested for various faults and system conditions in a test system. The software for the simulation is Digsilent Power factory. The results conclude that the quadrilateral distance relays experienced failures to detect faults in correct zone operation due to a weak source of DG. DG generates less fault current, as consequences, the relays see large impedances.

A Second Replicated Quantitative Analysis of Fault Distributions in Complex Software Systems

Background. Software engineering is in search for general principles that apply across contexts, for example to help guide software quality assurance. Fenton and Ohlsson presented such observations on fault distributions, which have been replicated once. Objectives.We intend to replicate their study a second time in a new environment. Method.We conducted a close replication, collecting defect data from five consecutive releases of a large software system in the telecommunications domain, and conducted the same analysis as in the original study. Results. The replication confirms results on un-evenly distributed faults over modules, and that fault proneness distribution persist over test phases. Size measures are not useful as predictors of fault proneness, while fault densities are of the same order of magnitude across releases and contexts. Conclusions. This replication confirms that the un-even distribution of defects motivates un-even distribution of quality assurance efforts, although predictors for such distribution of efforts are not sufficiently precise

Comparing the effectiveness of testing methods in improving programs: the effect of variations in program quality

We compare the efficacy of different testing methods for improving the reliability of software. Specifically, we use modelling to compare “operational” testing, in which test cases are chosen according to their probability of occurring in actual use of the software, against “debug” testing methods, in which the testers look for test cases which they consider likely to cause failure, or that satisfy some coverage criterion. We base our comparisons on the reliability reached by the program at the end of testing. Differently from previous studies, we consider the probability distribution of the achieved reliability, and thus the probability of satisfying specific requirements, rather than just the average reliability achieved. We take account of two sources of variation. The variation between the actual test histories that are possible for a given program and a given test method: and the fact that different programs start testing with different faults and initial reliability levels. By necessity, we use very simplified models of reality. Yet, we can show some interesting conclusions with important practical consequences. In general, there are stronger arguments in favor of operational testing than previous studies have show

SRAT-Distribution Voltage Sags and Reliability Assessment Tool

Interruptions to supply and sags of distribution system voltage are the main aspects causing customer complaints. There is a need for analysis of supply reliability and voltage sag to relate system performance with network structure and equipment design parameters. This analysis can also give prediction of voltage dips, as well as relating traditional reliability and momentary outage measures to the properties of protection systems and to network impedances. Existing reliability analysis software often requires substantial training, lacks automated facilities, and suffers from data availability. Thus it requires time-consuming manual intervention for the study of large networks. A user-friendly sag and reliability assessment tool (SRAT) has been developed based on existing impedance data, protection characteristics, and a model of failure probability. The new features included in SRAT are a) efficient reliability and sag assessments for a radial network with limited loops, b) reliability evaluation associated with realistic protection and restoration schemes, c) inclusion of momentary outages in the same model as permanent outage evaluation, d) evaluation of the sag transfer through meshed subtransmission network, and e) simplified probability distribution model determined from available faults records. Examples of the application of the tools to an Australian distribution network are used to illustrate the application of this model

Forecasting of Object-Oriented Faults

International audienceObject-Oriented Technologies, such as Java, provide efficient features to develop software applications. In particular, they allow the development costs to be reduced. However, issues highlighted by the “Object- Oriented Technology in Aviation” group have to be handled to guarantee a high level of safety, in order to use such technologies in avionics software. In particular, the risk of Object-Oriented Technologies design faults has to be reduced to an acceptable level. These risk reduction actions must be preceded by forecasting the actual risk level of the developed application. The paper aims at presenting a method used to forecast the risk of the presence of these Object-Oriented Technologies faults in a given program. The approach proposed is based on Bayesian networks. Its principles are introduced. It is illustrated on an example of faults: the Accidental Overriding (AO). We highlight that our approach takes into account the complex relationships existing between the various object-oriented features: inheritance, distribution of the attributes and methods, etc. To conclude, we show how the obtained data can be analysed to specify design guidelines allowing an acceptable risk level to be reached