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Constructing a safety case for automatically generated code from formal program verification

Constructing a safety case for automatically generated code from formal program verification
Constructing a safety case for automatically generated code from formal program verification
Formal methods can in principle provide the highest levels of assurance of code safety by providing formal proofs as explicit evidence for the assurance claims. However, the proofs are often complex and difficult to relate to the code, in particular if it has been generated automatically. They may also be based on assumptions and reasoning principles that are not justified. This causes concerns about the trustworthiness of the proofs and thus the assurance claims. Here we present an approach to systematically construct safety cases from information collected during a formal verification of the code, in particular from the construction of the logical annotations necessary for a formal, Hoare-style safety certification. Our approach combines a generic argument that is instantiated with respect to the certified safety property (i.e., safety claims) with a detailed, program-specific argument that can be derived systematically because its structure directly follows the course the annotation construction takes through the code. The resulting safety cases make explicit the formal and informal reasoning principles, and reveal the top-level assumptions and external dependencies that must be taken into account. However, the evidence still comes from the formal safety proofs. Our approach is independent of the given safety property and program, and consequently also independent of the underlying code generator. Here, we illustrate it for the AutoFilter system developed at NASA Ames.
249-62
Basir, N.
10c027b2-6fdd-46db-ab74-83d526522558
Denney, E.
ea98c398-f905-4e8f-8a1c-0a47b49e0abd
Fischer, B.
0c9575e6-d099-47f1-b3a2-2dbc93c53d18
Basir, N.
10c027b2-6fdd-46db-ab74-83d526522558
Denney, E.
ea98c398-f905-4e8f-8a1c-0a47b49e0abd
Fischer, B.
0c9575e6-d099-47f1-b3a2-2dbc93c53d18

Basir, N., Denney, E. and Fischer, B. (2008) Constructing a safety case for automatically generated code from formal program verification Computer Safety, Reliability, and Security. Proceedings 27th International Conference, SAFECOMP 2008, pp. 249-62.

Record type: Article

Abstract

Formal methods can in principle provide the highest levels of assurance of code safety by providing formal proofs as explicit evidence for the assurance claims. However, the proofs are often complex and difficult to relate to the code, in particular if it has been generated automatically. They may also be based on assumptions and reasoning principles that are not justified. This causes concerns about the trustworthiness of the proofs and thus the assurance claims. Here we present an approach to systematically construct safety cases from information collected during a formal verification of the code, in particular from the construction of the logical annotations necessary for a formal, Hoare-style safety certification. Our approach combines a generic argument that is instantiated with respect to the certified safety property (i.e., safety claims) with a detailed, program-specific argument that can be derived systematically because its structure directly follows the course the annotation construction takes through the code. The resulting safety cases make explicit the formal and informal reasoning principles, and reveal the top-level assumptions and external dependencies that must be taken into account. However, the evidence still comes from the formal safety proofs. Our approach is independent of the given safety property and program, and consequently also independent of the underlying code generator. Here, we illustrate it for the AutoFilter system developed at NASA Ames.

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More information

Published date: 2008
Additional Information: Imported from ISI Web of Science
Organisations: Electronic & Software Systems

Identifiers

Local EPrints ID: 269071
URI: http://eprints.soton.ac.uk/id/eprint/269071
PURE UUID: cc203ba2-cc41-4788-bb8f-8c26e40dc327

Catalogue record

Date deposited: 21 Apr 2010 07:46
Last modified: 18 Jul 2017 06:51

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Contributors

Author: N. Basir
Author: E. Denney
Author: B. Fischer

University divisions

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