Complex systems such as computers, aerospace systems, etc., are often tested by using a sequence of tests to exercise the functionality of the system. If the system fails a test, an error message is generated, initiating the test selection (TS) phase. The troubleshooter must decide whether or not to run more tests. Should the troubleshooter decide to conduct more tests, a test must be chosen as it may no longer be useful to conform to the predefined sequence. While in the TS phase, the troubleshooter will repeatedly make these decisions until he is done. The authors present a domain-independent framework to automate TS that is based on two computational models, TI and TP. Both models are needed for the authors show there are applications for which one model performs well, while the other model performs poorly. The use of the appropriate model for automating TS is indicated by certain characteristics of the testing sequence and the system under test.>

This paper presents fault-tolerant protocols for fast packet switch networks with convergence routing. The objective is to provide, after a link or a node (switch) failure, fast reconfiguration and continuous host-to-host communication. Convergence routing is a variant of deflection routing, which combines in a dynamic fashion, the on-line routing decision with the traffic load inside the network. Unlike other deflection techniques, convergence routing guarantees that packets will reach or converge to their destinations. This fault-tolerant solution is designed for a switch-based (i.e., arbitrary topology) LAN architecture called MetaNet. The original MetaNet's convergence routing scheme has been modified in order to facilitate the property that the packet header need not be recomputed after a failure and/or a reconfiguration. This is achieved by having, at the network interface, a translator that maps the unique destination address to a virtual address. The virtual addresses are stored at the packet header, and used for convergence routing, with a global sense of direction over (i) a single spanning tree, and (ii) over two edge-disjoint spanning trees, for redundancy (fault tolerance) and greater efficiency.>

The goal of software inspections and tests is to reduce the expected cost of software failure over the life of a product. This paper extends the use of defect triggers, the events which cause defects to be discovered, to help evaluate the effectiveness of inspection and test activities. In the case of inspections, the defect trigger is defined as a set of values which associate the skills of the inspector with the discovered defect. Similarly, for tests, the defect trigger values embody the various strategies being used in creating test scenarios. The usefulness of triggers in evaluating the effectiveness of software inspections and tests is demonstrated by evaluating the inspection and test activities of some software products. These evaluations are used to point to both deficiencies in inspection and test strategies, and progress made in improving such strategies.>

We present a case study of the use of a software process improvement method which is based on the analysis of defect data. The first step of the method is the classification of software defects using attributes which relate defects to specific process activities. Such classification captures the semantics of the defects in a fashion which is useful for process correction. The second step utilizes a machine-assisted approach to data exploration which allows a project team to discover such knowledge from defect data as is useful for process correction. We show that such analysis of defect data can readily lead a project team to improve their process during development.>

The goal of software inspection and test is to reduce the expected cost of software failure over the life of a product. The authors extend the use of defect triggers, the events that cause defects to be discovered, to help evaluate the effectiveness of inspections and test scenarios. In the case of inspections, the defect trigger is defined as a set of values that associate the skills of the inspector with the discovered defect. Similarly, for test scenarios, the defect trigger values embody the deferring strategies being used in creating these scenarios. The usefulness of triggers in evaluating the effectiveness of software inspections and tests is demonstrated by evaluating the inspection and test activities of some software products. These evaluations are used to point to deficiencies in inspection and test strategies, and to progress made in improving such strategies. The trigger distribution of the entire inspection or test series may then be used to highlight areas for further investigation, with the aim of improving the design, implementation, and test processes.>

Orthogonal defect classification (ODC), a concept that enables in-process feedback to software developers by extracting signatures on the development process from defects, is described. The ideas are evolved from an earlier finding that demonstrates the use of semantic information from defects to extract cause-effect relationships in the development process. This finding is leveraged to develop a systematic framework for building measurement and analysis methods. The authors define ODC and discuss the necessary and sufficient conditions required to provide feedback to a developer; illustrate the use of the defect type distribution to measure the progress of a product through a process; illustrate the use of the defect trigger distribution to evaluate the effectiveness and eventually the completeness of verification processes such as inspection or testing; provides sample results from pilot projects using ODC; and open the doors to a wide variety of analysis techniques for providing effective and fast feedback based on the concepts of ODC.>

Probe selection (PS) in machine diagnosis is viewed as a collection of models that apply under specific conditions. This makes it possible for three polynomial-time optimal algorithms to be developed for simplified PS models that allow different probes to have different costs. The work is compared with previous research, wherein H.A. Simon and J.B. Kadane (1975) review and develop a collection of models for optimal problem-solving search. The relationship between these models and the three newly developed algorithms for PS is explored. Two of the algorithms are unlike the ones discussed by Simon and Kadane. The third cannot be related to the problem-solving models.>

A simple and effective parallel algorithm to color the nodes of a graph is presented. The algorithm is useful in its own right. It also provides a vehicle to demonstrate the tradeoffs between performance and speed implicit in many parallel algorithms. The algorithm is used when the parallel machine has at least as many processors as there are nodes to color.>

The use of phase-locked clocks to limit clock skews to fractions of the clock period while keeping the algorithm overhead very small is investigated. The number of clocks in the system required to ensure that up to m arbitrary failures can be tolerated with all the good clocks still in synchrony has been shown to be N>or=3m+1. It is shown here that, if N>

Optimizing the design of real-time distributed systems is important since the systems are frequently critical to life. This optimization is a difficult problem, and heuristics and designer judgment are called for in the process. The chief cause of the difficulty is the large number of parameters under the designer's control which impact performance and life-cycle cost. We study the interplay between the more important parameters in this paper using two objective measures, i. e., the mean cost and the probability of dynamic failure in [6], [10]. Among these are the processor burn-in time and processor replacement policy. A central feature of this work is a look at how the application requirements affect the optimality of the distributed systems; indeed, the application requirements are an integral part of the analysis.