University of Minnesota
Software Engineering Center
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Darren Cofer

Recent Publications

Requirements Analysis of a Quad-Redundant Flight Control System

In this paper we detail our effort to formalize and prove requirements for the Quad-redundant Flight Control System (QFCS) within NASA’s Transport Class Model (TCM). We use a compositional approach with assume-guarantee contracts that correspond to the requirements for software components embedded in an AADL system architecture model. This approach is designed to exploit the verification effort and artifacts that are already part of typical software verification processes in the avionics domain.

Hierarchical Circular Compositional Reasoning

We describe a composition rule for hierarchically composed components that may involve circular reasoning between the components. It is similar to previous work by McMillan, specialized to component level reasoning. In contrast to McMillan's work, our composition rule can be used in provers that only support safety properties (e.g. k-induction model checkers) as long as the system and component contracts consist of state invariants. The composition rule still holds for richer contracts, but the resulting verification conditions then require a general purpose model checker.

Your "What" is My "How": Iteration and Hierarchy in System Design

Systems are naturally constructed in hierarchies, in which design choices made at higher levels of abstraction levy requirements on system components at the lower levels. Thus, whether an aspect of a system is a design choice or a requirement largely depends on your vantage point within the system components' hierarchy. Systems are also often constructed from the middle-out rather than top-down; compatibility with existing systems and architectures and availability of specific components influence high-level requirements.

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