In this paper, we propose an interactive segmentation method to apply user information during the segmentation of a specific anatomic structure. This method is formulated to use belief propagation to minimize a global cost function according to local level sets. The propagation starts with one user labeled point, and iteratively extends the user information from the labeled pixel to its neighborhood by calculating the beliefs of the pixels in the same level as the labeled pixel. Since the segmentation relies on both local user information and global image features, it is less interrupted by noise, and works well even the target is not obvious to its neighbor. The promising segmentation results also show that our method is robust to the objects with high shape variation and inhomogeneous intensity value appearance.

Many empirical studies in software engineering involve relationships between various process and product characteristics derived via linear regression analysis. We propose an alternative modeling approach using radial basis functions (RBFs) which provide a flexible way to generalize linear regression function. Further, RBF models possess strong mathematical properties of universal and best approximation. We present an objective modeling methodology for determining model parameters using our recent SG algorithm, followed by a model selection procedure based on generalization ability. Finally, we describe a detailed RBF modeling study for software effort estimation using a well-known NASA dataset.

No abstract available.

Discusses issues related to the design and and usage of database management systems consisting of massive amounts of data in parallel environments. The issues include the placement of the data in the memory, file systems, concurrent access to data, effects on query processing, the implications of specific machine architectures, and the peculiarities of specific parallel systems. Since not all parameters are currently amenable to rigorous analysis, results of performance studies are highlighted wherever they are deemed appropriate. >

An experimental study was undertaken to assess the improvement in program quality by using formal specifications. Specifications in the Z notation were developed for a simple but realistic anti-missile system. These specifications were then used to develop two versions in C by two programmers. Another set of three versions in Ada were independently developed from informal specifications in English. A comparison of the reliability of the resulting programs suggests the advantages of using formal specifications in terms of number of errors detected. Also, several errors that have been known to occur in earlier experiments dealing with this system were avoided by the use of formal specifications.>

There are a number of views as to what software reliability is and how it should be quantified. Some people believe that this measure should be binary in nature so that an imperfect program would have zero reliability while a perfect one would have a reliability value of one. This view parallels that of program proving whereby the program is either correct or incorrect. Others, however, feel that software reliability should be defined as the relative frequency of the times that the program works as intended by the user. This view is similar to that taken in testing where a percentage of the successful ewes is used as a measure of program quality. According to the latter viewpoint, software reliability is a probabilistic measure and can be defined as follows:

A number of analytical models have been proposed during the past 15 years for assessing the reliability of a software system. In this paper we present an overview of the key modeling approaches, provide a critical analysis of the underlying assumptions, and assess the limitations and applicability of these models during the software development cycle. We also propose a step-by-step procedure for fitting a model and illustrate it via an analysis of failure data from a medium-sized real-time command and control software system.

THIS is the second part of the special issue on Software Reliability. Part I was published in December 1985 and dealt with software reliability estimation, new modeling techniques, management issues, testing and verification, and fault-tolerant programs. Papers in this issue address software reliability models, hardware-software effects, fault-tolerant software mechanisms, experimental results on TV-version programming, and techniques for developing reliable software.

This paper deals with the problem of determining the optimum time when testing can stop and the system be considered ready for operational use. This decision, of course, depends on the model for the software failure phenomenon and the criterion used for evaluating system readiness. Using the non-homogeneous Poisson process model of Goel and Okumoto [4], two criteria are investigated, viz the software reliability and total expected cost. A simple cost model is developed and the optimum release policy, based on cost criterion, is derived. Numerical examples are used to illustrate the results.

In this paper we develop a model for the operational phase of a software system which incorporates the uncertainty of error removal and the time spent in correcting errors. Expressions for various measures of software performance, e.g. distribution of time to a specified number of remaining errors, the expected number of errors detected and corrected in time t, and software system availability are derived. Numerical examples are used to illustrate these results.