3092732
Inequality Constraints in Causal Models with Hidden Variables
We present a class of inequality constraints on the set of distributions induced by local interventions on variables governed by a causal Bayesian network, in which some of the variables remain unmeasured. We derive bounds on causal effects that are not directly measured in randomized experiments. We derive instrumental inequality type of constraints on nonexperimental distributions. The results have applications in testing causal models with observational or experimental data.
10434536
Identifying Linear Causal Effects
This paper concerns the assessment of linear cause-effect relationships from a combination of observational data and qualitative causal structures. The paper shows how techniques developed for identifying causal effects in causal Bayesian networks can be used to identify linear causal effects, and thus provides a new approach for assessing linear causal effects in structural equation models. Using this approach the paper develops a systematic procedure for recognizing identifiable direct causal effects.
18528442
Better Reliability Assessment and Prediction through Data Clustering
This paper presents a new approach to software reliability modeling by grouping data into clusters of homogeneous failure intensities. This series of data clusters associated with different time segments can be directly used as a piecewise linear model for reliability assessment and problem identification, which can produce meaningful results early in the testing process. The dual model fits traditional software reliability growth models (SRGMs) to these grouped data to provide long-term reliability assessments and predictions. These models were evaluated in the testing of two large software systems from IBM. Compared with existing SRGMs fitted to raw data, our models are generally more stable over time and produce more consistent and accurate reliability assessments and predictions.
16178189
Super-resolution Imaging Using Grid Computing
The super-resolution (SR) imaging is to overcome the inherent limitations of the image acquisition systems to produce high-resolution images from their low-resolution counterparts. In our recent work, the Markov chain Monte Carlo (MCMC) technique has been successfully developed and shown as a promising stochastic approach for addressing the SR problem. However, the MCMC SR approach requires substantial amounts of computational resources, for it not only needs to generate a huge number of samples, but also requires an exhaustive search for obtaining an optimal prior image model. To tackle the above computation challenge, Grid computing is introduced for tackling the SR problem in this paper. The computationally- intensive MCMC SR task is broke down into a set of independent and small sub-tasks, which are further distributed and implemented in the grid computing environment. Their respective results are finally assembled to produce a high-resolution image as the final result of the entire MCMC SR task. Experiments are conducted to show that grid computing can effectively accelerating the execution time of the MCMC SR algorithm.
46034477
Reliability Measurement, Analysis, and Improvement for Large Software Systems
Abstracts This chapter surveys recent developments in software reliability engineering, and presents results in measuring test activities, analyzing product reliability, and identifying high risk areas for focused reliability improvement for large software systems. Environmental constraints and existing analysis techniques are carefully examined to select appropriate analysis techniques, models, implementation strategies, and support tools suitable for large software systems. The analysis and modeling activities include measure definition, data gathering, graphical test activity and defect tracking, overall quality assessment using software reliability growth models, and identification of problematic areas and risk management using tree-based reliability models. Various existing software tools have been adapted and integrated to support these analysis and modeling activities. This approach has been used in the testing phase of several large software products developed in the IBM Software Solutions Toronto Laboratory and was demon- strated to be effective and efficient. Various practical problems and solutions in implementing this strategy are also discussed.
37297978
Analyzing and Improving Reliability: A Tree-Based Approach
Tree-based reliability models integrate the benefits of software reliability growth models and input domain reliability models, offering a framework to assess reliability and guidance to improve it. The authors studied five large systems to test their approach.
19924236
Test-Execution-Based Reliability Measurement and Modeling for Large Commercial Software
The paper studies practical reliability measurement and modeling for large commercial software systems based on test execution data collected during system testing. The application environment and the goals of reliability assessment were analyzed to identify appropriate measurement data. Various reliability growth models were used on failure data normalized by test case executions to track testing progress and provide reliability assessment. Practical problems in data collection, reliability measurement and modeling, and modeling result analysis were also examined. The results demonstrated the feasibility of reliability measurement in a large commercial software development environment and provided a practical comparison of various reliability measurements and models under such an environment. >