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Easterbrook, Steve

Publications and source records attributed to Easterbrook, Steve.

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Model Checking Verification and Validation at JPL and the NASA Fairmont IV and V Facility

We show how a technology transfer effort was carried out. The successful use of model checking on a pilot JPL flight project demonstrates the usefulness and the efficacy of the approach. The pilot project was used to model a complex spacecraft controller. Software design and implementation validation were carried out successfully. To suggest future applications we also show how the implementation validation step can be automated. The effort was followed by the formal introduction of the modeling technique as a part of the JPL Quality Assurance process.

Schneider, Frank↗
NASA NTRS1997

Experiences Using Lightweight Formal Methods for Requirements Modeling

This paper describes three case studies in the lightweight application of formal methods to requirements modeling for spacecraft fault protection systems. The case studies differ from previously reported applications of formal methods in that formal methods were applied very early in the requirements engineering process, to validate the evolving requirements. The results were fed back into the projects, to improve the informal specifications. For each case study, we describe what methods were applied, how they were applied, how much effort was involved, and what the findings were. In all three cases, formal methods enhanced the existing verification and validation processes, by testing key properties of the evolving requirements, and helping to identify weaknesses. We conclude that the benefits gained from early modeling of unstable requirements more than outweigh the effort needed to maintain multiple representations.

Easterbrook, Steve↗
NASA NTRS1997

Formal Methods for Verification and Validation of Partial Specifications: A Case Study

This paper describes our work exploring the suitability of formal specification methods for independent verification and validation (IV&V) of software specifications for large, safety critical systems. An IV&V contractor often has to perform rapid analysis on incomplete specifications, with no control over how those specifications are represented. Lightweight formal methods show significant promise in this context, as they offer a way of uncovering major errors, without the burden of full proofs of correctness. We describe a case study of the use of partial formal models for V&V of the requirements for Fault Detection Isolation and Recovery on the space station. We conclude that the insights gained from formalizing a specification are valuable, and it is the process of formalization, rather than the end product that is important. It was only necessary to build enough of the formal model to test the properties in which we were interested. Maintenance of fidelity between multiple representations of the same requirements (as they evolve) is still a problem, and deserves further study.

Easterbrook, Steve↗
NASA NTRS1997

Formal Methods of V&V of Partial Specifications: An Experience Report

This paper describes our work exploring the suitability of formal specification methods for independent verification and validation (IV&V) of software specifications for large, safety critical systems. An IV&V contractor often has to perform rapid analysis on incomplete specifications, with no control over how those specifications are represented. Lightweight formal methods show significant promise in this context, as they offer a way of uncovering major errors, without the burden of full proofs of correctness. We describe an experiment in the application of the method SCR. to testing for consistency properties of a partial model of requirements for Fault Detection Isolation and Recovery on the space station. We conclude that the insights gained from formalizing a specification is valuable, and it is the process of formalization, rather than the end product that is important. It was only necessary to build enough of the formal model to test the properties in which we were interested. Maintenance of fidelity between multiple representations of the same requirements (as they evolve) is still a problem, and deserves further study.

Easterbrook, Steve↗
NASA NTRS1996

Experiences Using Formal Methods for Requirements Modeling

This paper describes three cases studies in the lightweight application of formal methods to requirements modeling for spacecraft fault protection systems. The case studies differ from previously reported applications of formal methods in that formal methods were applied very early in the requirements engineering process, to validate the evolving requirements. The results were fed back into the projects, to improve the informal specifications. For each case study, we describe what methods were applied, how they were applied, how much effort was involved, and what the findings were. In all three cases, the formal modeling provided a cost effective enhancement of the existing verification and validation processes. We conclude that the benefits gained from early modeling of unstable requirements more than outweigh the effort needed to maintain multiple representations.

Easterbrook, Steve↗
NASA NTRS1996

Communication Problems in Requirements Engineering: A Field Study

The requirements engineering phase of software development projects is characterized by the intensity and importance of communication activities. During this phase, the various stakeholders must be able to communicate their requirements to the analysts, and the analysts need to be able to communicate the specifications they generate back to the stakeholders for validation. This paper describes a field investigation into the problems of communication between disparate communities involved in the requirements specification activities. The results of this study are discussed in terms of their relation to three major communication barriers: (1) ineffectiveness of the current communication channels; (2) restrictions on expressiveness imposed by notations; and (3) social and organizational barriers. The results confirm that organizational and social issues have great influence on the effectiveness of communication. They also show that in general, end-users find the notations used by software practitioners to model their requirements difficult to understand and validate.

Al-Rawas, Amer↗
NASA NTRS1996

Learning from Inconsistency

This position paper argues that inconsistencies that occur during the development of a software specification offer an excellent way of learning more about the development process. We base this argument on our work on inconsistency management. Much attention has been devoted recently to the need to allow inconsistencies to occur during software development, to facilitate flexible development strategies, especially for collaborative work. Recent work has concentrated on reasoning in the presence of inconsistency, tracing inconsistencies with 'pollution markers' and supporting resolution. We argue here that one of the most important aspects of inconsistency is the learning opportunity it provides. We are therefore concerned with how to capture this learning outcome so that its significance is not lost. We present a small example of how apprentice software engineers learn from their mistakes, and outline how an inconsistency management tool could support this learning. We then argue that the approach can be used more generally as part of continuous process improvement.

Easterbrook, Steve↗
NASA NTRS1996

The Role of Independent V&V in Upstream Software Development Processes

This paper describes the role of Verification and Validation (V&V) during the requirements and high level design processes, and in particular the role of Independent V&V (IV&V). The job of IV&V during these phases is to ensure that the requirements are complete, consistent and valid, and to ensure that the high level design meets the requirements. This contrasts with the role of Quality Assurance (QA), which ensures that appropriate standards and process models are defined and applied. This paper describes the current state of practice for IV&V, concentrating on the process model used in NASA projects. We describe a case study, showing the processes by which problem reporting and tracking takes place, and how IV&V feeds into decision making by the development team. We then describe the problems faced in implementing IV&V. We conclude that despite a well defined process model, and tools to support it, IV&V is still beset by communication and coordination problems.

Easterbrook, Steve↗
NASA NTRS1996

Independent Validation of Specifications: A Coordination Headache

Large, complex projects face significant barriers to coordination and communication due to continuous, rapid changes during a project's life cycle. Such changes must be tracked, analyzed, and reconciled to ensure high quality in the end product, otherwise problems may get lost or ignored in the overall complexity. We report on 'work-in-progress' in the study of coordination problems between two independent, separate groups: software development and software analysis. We have begun to construct a taxonomy of coordination problems, which we illustrate with two scenarios. We briefly describe current attempts to introduce incremental improvements to coordination problems in such projects via World Wide Web tools. Based on actual project experiences, we plan to deploy such tools in a non-intrusive fashion to improve coordination and communication between software development groups.

Easterbrook, Steve↗