The study of defects is a principal topic of software systems, af-fecting all phases of a system's lifecycle. Defects are the cause of errors and service degradations. Unresolved errors cause failures. If defects cannot be prevented effectively, then error control me-chanisms must be evaluated. We introduce a model to distinguish between defects, errors, and service degradations. A two-dimensional classification scheme is developed for defects, defined by the types of process interaction and software corruption that are involved. A third dimension is added to this taxonomy for defects that cause service degradation, based on the deviations in service quality that are tolerated. We investigate the role of service degradation in error prevention.

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In a previous paper we discussed resource deadlock within a classification of all dead states. We differentiated between the different types of anomalies that are called deadlock in the computer science literature. Our primary aim was to correct inconsistencies that are currently being taught in operating systems' textbooks. We introduced a model that allowed us to precisely define deadlock, but we only provided a partial definition of resource deadlock, which, as we noted, was limited to deadlocks with uniquely identifiable resource units. In response to readers of OSR, we now distinguish between different types of resource deadlock and provide a comprehensive definition. We also suggest that it may be desirable to maintain separate definitions.

This paper is a call to SIGAda members to make a determined thrust to broaden Ada usage in the commercial world. More specifically, we wish to exploit an opportunity in the Electronic Design Automation industry (EDA) to use (a kernel of) Ada as a hardware description language (HDL) for the design and programming of today's System On a Chip (SOC). The Ada subset referred to in this paper is intended for the EDA domain to solve practical problems as an HDL, and, in addition, as the interfacing programming language used for testing and simulations (a market currently dominated by C/C++). Simplicity can be a significant aid in penetrating the market of users and makers of EDA tools. This community consists mostly of electrical engineers and tool manufacturers who would have both a cultural orientation and a commercial interest in a simple kernel of Ada.We use examples to illustrate the appropriateness of Kernel Ada for the development and testing of reusable hardware components.