A traditional assurance case employs a positive argument in which reasoning
steps, grounded on evidence and assumptions, sustain a top claim that has
external significance. Human judgement is required to check the evidence, the
assumptions, and the narrative justifications for the reasoning steps; if all
are assessed good, then the top claim can be accepted.
A valid concern about this process is that human judgement is fallible and
prone to confirmation bias. The best defense against this concern is vigorous
and skeptical debate and discussion in the manner of a dialectic or Socratic
dialog. There is merit in recording aspects of this discussion for the benefit
of subsequent developers and assessors. Defeaters are a means doing this: they
express doubts about aspects of the argument and can be developed into subcases
that confirm or refute the doubts, and can record them as documentation to
assist future consideration.
This report describes how defeaters, and multiple levels of defeaters, should
be represented and assessed in Assurance 2.0 and its Clarissa/ASCE tool
support. These mechanisms also support eliminative argumentation, which is a
contrary approach to assurance, favored by some, that uses a negative argument
to refute all reasons why the top claim could be false.

描述了在 Assurance 2.0 及其 Clarissa/ASCE 工具支持下如何表示和评估 defeaters 和多个层次的 defeaters。这些机制还支持消除性论证，这是一种与确保相反的方法，被一些人青睐，它使用负面论证来否定为什么顶层主张可能是错误的所有理由。

保障 2.0 中的挑战与否定性论证

Defeaters and Eliminative Argumentation in Assurance 2.0

An assurance case has become an integral component for the certification of
safety-critical systems. While manually defining assurance case patterns can be
not avoided, system-specific instantiations of assurance case patterns are both
costly and time-consuming. It becomes especially complex to maintain an
assurance case for a system when the requirements of the System-Under-Assurance
change, or an assurance claim becomes invalid due to, e.g., degradation of a
systems component, as common when deploying learning-enabled components. In
this paper, we report on our preliminary experience leveraging the tool
integration framework Evidential Tool Bus (ETB) for the construction and
continuous maintenance of an assurance case from a predefined assurance case
pattern. Specifically, we demonstrate the assurance process on an industrial
Automated Valet Parking system from the automotive domain. We present the
formalization of the provided assurance case pattern in the ETB processable
logical specification language of workflows. Our findings show that ETB is able
to create and maintain evidence required for the construction of an assurance
case.

借助 Evidential Tool Bus（ETB）工具集成框架，本文报道了使用预定义的保证案例模式从事保证案例的构建和持续维护的初步经验，以满足安全关键系统的认证需求。

面向 Evidential 工具总线的 ADS 连续保证案例创建

Towards Continuous Assurance Case Creation for ADS with the Evidential  Tool Bus

An assurance case is intended to provide justifiable confidence in the truth
of its top claim, which typically concerns safety or security. A natural
question is then "how much" confidence does the case provide? We argue that
confidence cannot be reduced to a single attribute or measurement. Instead, we
suggest it should be based on attributes that draw on three different
perspectives: positive, negative, and residual doubts.
Positive Perspectives consider the extent to which the evidence and overall
argument of the case combine to make a positive statement justifying belief in
its claims. We set a high bar for justification, requiring it to be
indefeasible. The primary positive measure for this is soundness, which
interprets the argument as a logical proof. Confidence in evidence can be
expressed probabilistically and we use confirmation measures to ensure that the
"weight" of evidence crosses some threshold. In addition, probabilities can be
aggregated from evidence through the steps of the argument using probability
logics to yield what we call probabilistic valuations for the claims.
Negative Perspectives record doubts and challenges to the case, typically
expressed as defeaters, and their exploration and resolution. Assurance
developers must guard against confirmation bias and should vigorously explore
potential defeaters as they develop the case, and should record them and their
resolution to avoid rework and to aid reviewers.
Residual Doubts: the world is uncertain so not all potential defeaters can be
resolved. We explore risks and may deem them acceptable or unavoidable. It is
crucial however that these judgments are conscious ones and that they are
recorded in the assurance case.
This report examines the perspectives in detail and indicates how Clarissa,
our prototype toolset for Assurance 2.0, assists in their evaluation.

这篇文章主要讨论了保证案例的可靠性评估和其提供的信任程度，其信任程度不能简单化为单一的属性或测量，并应基于积极、消极和残留疑虑这三个不同的属性。