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Enhancing the Maintainability of Safety Cases Using Safety Contracts
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. (Software Engineering)ORCID iD: 0000-0002-9347-1949
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Safety critical systems are those systems whose failure could result in loss of life, significant property damage, or damage to the environment. These systems require high quality and dependability levels in them, where system safety is a major property that should be adequately assured to avoid any severe outcomes. Many safety critical systems in different domains (e.g., avionics, railway, automotive, etc.) are subject to a certification. The certification process is based on an evaluation of whether the associated hazards to a system are mitigated to an acceptable level. Safety cases are often required to demonstrate how a regulatory body can reasonably conclude that a system is acceptably safe from the evidence available. The development of safety cases has become common practice in many safety critical system domains. However, safety cases are costly since they need significant amount of time and efforts to produce. This cost can be dramatically increased (even for already certified systems) due to system changes as they require maintaining the safety case before it can be submitted for certification. Anticipating potential changes is useful since it reveals traceable consequences that will eventually reduce the maintenance efforts. However, considering a complete list of anticipated changes is difficult. What can be easier though is to determine the flexibility of system components to changes.

Sensitivity analysis has been proposed as a useful tool to measure the flexibility of the different system properties to changes. Furthermore, the concept of contracts have been proposed as a means for facilitating the change management process due to their ability to record the dependencies among system's components. In this thesis, we use sensitivity analysis to support changes prediction and prioritisation. We also use safety contracts to record the information of changes that will ultimately advise the engineers what to consider and check when changes actually happen.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2015.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 220
National Category
Software Engineering
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-29133ISBN: 978-91-7485-238-7 (print)OAI: oai:DiVA.org:mdh-29133DiVA: diva2:856720
Presentation
2015-11-13, Mälardalens högskola, Delta, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2015-10-07 Created: 2015-09-25 Last updated: 2015-11-09Bibliographically approved
List of papers
1. Deriving Safety Contracts to Support Architecture Design of Safety Critical Systems
Open this publication in new window or tab >>Deriving Safety Contracts to Support Architecture Design of Safety Critical Systems
2015 (English)In: Proceedings of IEEE International Symposium on High Assurance Systems Engineering, 2015, Vol. january, 126-133 p.Conference paper, (Refereed)
Abstract [en]

The use of contracts to enhance the maintainability of safety-critical systems has received a significant amount of research effort in recent years. However some key issues have been identified: the difficulty in dealing with the wide range of properties of systems and deriving contracts to capture those properties; and the challenge of dealing with the inevitable incompleteness of the contracts. In this paper, we explore how the derivation of contracts can be performed based on the results of failure analysis. We use the concept of safety kernels to alleviate the issues. Firstly the safety kernel means that the properties of the system that we may wish to manage can be dealt with at a more abstract level, reducing the challenges of representation and completeness of the “safety” contracts. Secondly the set of safety contracts is reduced so it is possible to reason about their satisfaction in a more rigorous manner.

National Category
Computer and Information Science
Identifiers
urn:nbn:se:mdh:diva-27904 (URN)10.1109/HASE.2015.27 (DOI)000380911000016 ()2-s2.0-84936877188 (Scopus ID)978-1-4799-8111-3 (ISBN)
Conference
6th IEEE International Symposium on High Assurance Systems Engineering, HASE 2015; Daytona Beach; United States; 8 January 2015 through 10 January 2015; Category numberE5428; Code 112813
Projects
SYNOPSIS - Safety Analysis for Predictable Software Intensive SystemsSafeCer - Safety Certification of Software-Intensive Systems with Reusable Components
Available from: 2015-04-26 Created: 2015-04-26 Last updated: 2016-10-31Bibliographically approved
2. An Approach to Maintaining Safety Case Evidence After A System Change
Open this publication in new window or tab >>An Approach to Maintaining Safety Case Evidence After A System Change
2014 (English)In: 2014 Tenth European Dependable Computing Conference EDCC 2014, 2014Conference paper, (Refereed)
Abstract [en]

Developers of some safety critical systems construct a safety case. Developers changing a system during development or after release must analyse the change's impact on the safety case. Evidence might be invalidated by changes to the system design, operation, or environmental context. Assumptions valid in one context might be invalid elsewhere. The impact of change might not be obvious. This paper proposes a method to facilitate safety case maintenance by highlighting the impact of changes.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-26425 (URN)9781479938056 (ISRN)
Conference
2014 Tenth European Dependable Computing Conference EDCC 2014, 13-16 May 2014, Newcastle, United Kingdom
Available from: 2014-11-02 Created: 2014-10-31 Last updated: 2015-10-07Bibliographically approved
3. Using Sensitivity Analysis to Facilitate The Maintenance of Safety Cases
Open this publication in new window or tab >>Using Sensitivity Analysis to Facilitate The Maintenance of Safety Cases
2015 (English)In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) / [ed] Juan Antonio de la Puente, Tullio Vardanega, 2015, Vol. 9111, 162-176 p.Conference paper, (Refereed)
Abstract [en]

A safety case contains safety arguments together with supporting evidence that together should demonstrate that a system is acceptably safe. System changes pose a challenge to the soundness and cogency of the safety case argument. Maintaining safety arguments is a painstaking process because it requires performing a change impact analysis through interdependent elements. Changes are often performed years after the deployment of a system making it harder for safety case developers to know which parts of the argument are affected. Contracts have been proposed as a means for helping to manage changes. There has been significant work that discusses how to represent and to use them but there has been little on how to derive them. In this paper, we propose a sensitivity analysis approach to derive contracts from Fault Tree Analyses and use them to trace changes in the safety argument, thus facilitating easier maintenance of the safety argument. 

Series
Lecture Notes in Computer Science, ISSN 0302-9743
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Computer Systems
Identifiers
urn:nbn:se:mdh:diva-29130 (URN)10.1007/978-3-319-19584-1_11 (DOI)2-s2.0-84947983647 (Scopus ID)978-3-319-19583-4 (ISBN)
Conference
20th Ada-Europe International Conference on Reliable Software Technologies, Madrid Spain, June 22-26, 2015.
Available from: 2015-09-25 Created: 2015-09-25 Last updated: 2015-12-04Bibliographically approved
4. Facilitating the Maintenance of Safety Cases
Open this publication in new window or tab >>Facilitating the Maintenance of Safety Cases
2015 (English)In: The 3rd International Conference on Reliability, Safety and Hazard - Advances in Reliability, Maintenance and Safety ICRES-ARMS'15, 2015Conference paper, (Refereed)
National Category
Engineering and Technology Computer Systems
Identifiers
urn:nbn:se:mdh:diva-28147 (URN)
Conference
The 3rd International Conference on Reliability, Safety and Hazard - Advances in Reliability, Maintenance and Safety ICRES-ARMS'15, 1-4 Jun 2015, Luleå, Sweden
Projects
SYNOPSIS - Safety Analysis for Predictable Software Intensive Systems
Available from: 2015-06-09 Created: 2015-06-08 Last updated: 2015-10-07Bibliographically approved
5. Deriving Hierarchical Safety Contracts
Open this publication in new window or tab >>Deriving Hierarchical Safety Contracts
2016 (English)In: Proceedings: 2015 IEEE 21st Pacific Rim International Symposium on Dependable Computing, PRDC 2015, 2016, Vol. jan, 119-128 p.Conference paper, (Refereed)
Abstract [en]

Safety cases need significant amount of time and effort to produce. The required amount of time and effort can be dramatically increased due to system changes as safety cases should be maintained before they can be submitted for certification or re-certification. Anticipating potential changes is useful since it reveals traceable consequences that will eventually reduce the maintenance efforts. However, considering a complete list of anticipated changes is difficult. What can be easier though is to determine the flexibility of system components to changes. Using sensitivity analysis is useful to measure the flexibility of the different system properties to changes. Furthermore, contracts have been proposed as a means for facilitating the change management process due to their ability to record the dependencies among system’s components. In this paper, we extend a technique that uses a sensitivity analysis to derive safety contracts from Fault Tree Analyses (FTA) and uses these contracts to trace changes in the safety argument. The extension aims to enabling the derivation of hierarchical and correlated safety contracts.We motivate the extension through an illustrative example within which we identify limitations of the technique and discuss potential solutions to these limitations. 

National Category
Electrical Engineering, Electronic Engineering, Information Engineering Computer Systems
Identifiers
urn:nbn:se:mdh:diva-29131 (URN)10.1109/PRDC.2015.21 (DOI)000380403300013 ()2-s2.0-84964371811 (Scopus ID)978-146739376-8 (ISBN)
Conference
21st IEEE Pacific Rim International Symposium on Dependable Computing, PRDC 2015; Zhangjiajie; China; 18 November 2015 through 20 November 2015; Category numberE5673; Code 118981
Available from: 2015-09-25 Created: 2015-09-25 Last updated: 2016-08-18Bibliographically approved

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