The various papers record the evolution of my thinking on the topic of assurance cases. The first is this Technical Report, which is updated from my part of a NASA Contractor Report developed with colleagues at Boeing. I think sections 2, 3, and 4 remain useful; they document, respectively, the origin and history of safety and assurance cases, how a section of DO-178C might be interpreted as an assurance case, and something of the notations and tools available (in 2015). Section 5, on evaluation of assurance cases, is still OK, especially for background on logic and related topics, but my thinking has developed since then.

My current thinking is that the leaves and the interior parts of an
assurance case argument (viewed as a tree) should be interpreted
differently from each other. The leaves concern *evidence* about the system
and are best evaluated using methods from *epistemology*,
whereas the interior nodes document *reasoning* (based on the
evidence) and should be evaluated by the methods of *logic*.
This idea is first adumbrated in my
SafeComp 2013 paper.

A detailed proposal and example how evidential steps can be evaluated
using the ideas and measures of Bayesian *confirmation theory* is
developed in my AAA 2015 paper,
and a comparable treatment for reasoning steps is developed in my
forthcoming Shonan 2016
paper, which builds on the epistemological notion
of *indefeasibility*.

Together, these two approaches provide an interpretation for assurance
case arguments that is a systematic version of *Natural Language
Deductivism* (NLD), as documented in my
Marktoberdorf 2016
paper. NLD is the idea that an assurance case should provide a
deductively valid argument; it differs from deductive proof in formal
mathematics and logic in that its premises are "reasonable or
plausible" rather than certain, and hence its conclusions are likewise
reasonable or plausible rather than certain. The criteria of AAA 2015
systematize what it means for the premises to be "reasonable or
plausible."

The Marktoberdorf 2016 paper was written before the Shonan 2016 paper and so it is not quite the best overall summary: for that, I suggest reading the AAA 2015 and Shonan 2016 papers for detail on evidential and reasoning steps, respectively, and the Marktoberdorf 2016 paper for the overall picture.

Please note that many of the papers here are slightly updated from their published form--so it's always best to get my papers from my bibliography page.

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