Isabelle/SACM: Computer-Assisted Assurance Cases with Integrated Formal Methods

Abstract

Assurance cases (ACs) are often required to certify critical systems. The use of integrated formal methods (FMs) in assurance can improve automation, increase confidence, and overcome errant reasoning. However, ACs can rarely be fully formalised, as the use of FMs is contingent on models that are validated by informal processes. Consequently, assurance techniques should support both formal and informal artifacts, with explicated inferential links between them. In this paper, we contribute a formal machine-checked interactive language for the computer-assisted construction of ACs called Isabelle/SACM. The framework guarantees well-formedness, consistency, and traceability of ACs, and allows a tight integration of formal and informal evidence of various provenance. To validate Isabelle/SACM, we present a novel formalisation of the Tokeneer benchmark, verify its security requirements, and form a mechanised AC that combines the resulting formal and informal artifacts.

Population-induced phase transitions and the verification of chemical reaction networks

“…It is likely that evidence that such systems behave as intended will be required for certification by regulators prior to deployment. Toward providing such evidence, Nemouchi et al have recently shown how a descriptive language for safety cases can be incorporated into Isabelle in order to formalize argument-based safety assurance cases [38].…”

Towards Certified Analysis of Software Product Line Safety Cases

“…The algorithm starts by restricting the traceability relation based on D, slices the original system model S using the elements deleted and modified as a slicing criterion, and slices the modified system model S using the added and modified elements as the slicing criterion (lines [16][17][18]. Using those two slices, the corresponding GSN model elements are traced using the traceability relation (line 19). The GSN elements traced from elements deleted from the original system model are to be revised (line 20).…”

“…The seL4 microkernel [14] was verified using the Isabelle\HOL theorem prover. Isabelle was also used to formalize the Structured Assurance Case Metamodel (SACM) notation for certified definition of assurance cases [19].…”