Completeness, robustness, and safety in real-time software requirements specification

This paper presents an approach to providing a rigorous basis for ascertaining whether or not a given set of software requirements is internally complete, i.e., closed with respect to questions and inferences that can be made on the basis of information included in the specification. Emphasis is placed on aspects of software requirements specifications that previously have not been adequately handled, including timing abstractions, safety, and robustness

Modeling the external software interface for requirements specification

Requirements specification is an important part of the software, indeed the system, development process. It is critical that this effort be started early. This work suggests an early model for software developers to incorporate a systems viewpoint in their process. This model is an attempt to formalize an approach that will include a systematic representation of essentials of the external interface for software that is embedded within a larger system. The model is useful for early analysis of the software system and environment for such things as consistency, completeness, and safety

Application of Safety Verification Methodology Framework During Software Development Phases

In order to detect and prevent faults, researchers have developed safety standards, safety analysis techniques, and fault-tolerant techniques; however, there are still no methodology frameworks for verifying safety-critical software systems. This research’s methodology combines software-safety methods into a comprehensive whole for the purpose of verifying safety-critical software systems. This research concentrated on developing a methodology framework that combines static-verification, dynamic-verification, and fault-tolerant concepts for verifying safety-critical software systems

Independent verification of specification models for large software systems at the early phases of development lifecycle

One of the major challenges facing the software industry, in general and IV&V (Independent Verification and Validation) analysts in particular, is to find ways for analyzing dynamic behavior of requirement specifications of large software systems early in the development lifecycle. Such analysis can significantly improve the performance and reliability of the developed systems. This dissertation addresses the problem of developing an IV&V framework for extracting semantics of dynamic behavior from requirement specifications based on: (1) SART (Structured Analysis with Realtime) models, and (2) UML (Unified Modeling Language) models.;For SART, the framework presented here shows a direct mapping from SART specification models to CPN (Colored Petrinets) models. The semantics of the SART hierarchy at the individual levels are preserved in the mapping. This makes it easy for the analyst to perform the analysis and trace back to the corresponding SART model. CPN was selected because it supports rigorous dynamic analysis. A large scale case study based on a component of NASA EOS system was performed for a proof of the concept.;For UML specifications, an approach based on metamodels is presented. A special type of metamodel, called dynamic metamodel (DMM), is introduced. This approach holds several advantages over the direct mapping of UML to CPN. The mapping rules for generating DMM are not CPN specific, hence they would not change if a language other than CPN is used. Also it makes it more flexible to develop DMM because other types of models can be added to the existing UML models. A simple example of a pacemaker is used to illustrate the concepts of DMM

Completeness, robustness, and safety in real-time software requirements specification

This paper presents an approach to providing a rigorous basis for ascertaining whether or not a given set of software requirements is internally complete, i.e., closed with respect to questions and inferences that can be made on the basis of information included in the specification. Emphasis is placed on aspects of software requirements specifications that previously have not been adequately handled, including timing abstractions, safety, and robustness

Formal methods and digital systems validation for airborne systems

This report has been prepared to supplement a forthcoming chapter on formal methods in the FAA Digital Systems Validation Handbook. Its purpose is as follows: to outline the technical basis for formal methods in computer science; to explain the use of formal methods in the specification and verification of software and hardware requirements, designs, and implementations; to identify the benefits, weaknesses, and difficulties in applying these methods to digital systems used on board aircraft; and to suggest factors for consideration when formal methods are offered in support of certification. These latter factors assume the context for software development and assurance described in RTCA document DO-178B, 'Software Considerations in Airborne Systems and Equipment Certification,' Dec. 1992

A framework for the requirements analysis of safety-critical computing systems

PhD ThesisDigital computers are increasingly being used in safety-critical applications (e.g., avionics, chemical plant and railway systems). The main motivations for introducing computers into such environments are to increase performance, flexibility and efficiency. However, the cost to safety in achieving these benefits using computing systems is unclear. The general class of systems considered in this thesis are process control systems. More specifically the thesis examines the class of safety-critical computing systems which are a component of a process control system that could cause or allow the overall system to enter into a hazardous state. This thesis investigates the role oiformal methods in safety-critical computing systems. The phase of system development considered is requirements analysis. Experience in safety-critical systems has shown that errors in the identified requirements are one of the major causes of mishap. It is argued that to gain a complete understanding of such computing systems, the requirements of the overall system and the properties of the environment must be analyzed in a common formal framework. A system development model based on the separation of safety and mission issues is discussed, which highlights the essential specifications that must be produced during requirements analysis. A formal model for the representation of these essential specifications is presented. The semantics of this formal model are based on the notion of a system history. To structure the specifications expressed by this formal model the concept of a mode is introduced. This thesis suggests that for a formal model to be useful during requirements analysis a related systematic methodology, which provides comprehensive guidelines for the analysts who use the model must be made available. An appropriate methodology, based upon the system development model, which incorporates some traditional system safety techniques is described. Overall, the thesis presents a framework for requirements analysis by providing a system development model, formal model and related development methodology. An example of how this framework can support requirements analysis is presented in the appendices Band C.UK Science and Engineering Research Council: Alvey Software Reliability Project Grant