What does a Conditional Knowledge Base Entail?
What does a Conditional Knowledge Base Entail?
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DOI：
10.1016/0004-3702(92)90041-u
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发表时间：
1989-12
期刊：
影响因子：
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通讯作者：
D. Lehmann;M. Magidor
中科院分区：
文献类型：
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作者：
D. Lehmann;M. Magidor
本文提出了一种基于非单调结果关系概念的非单调推理的逻辑方法。条件知识库由一组 if … then … 类型的条件断言组成，代表代理拥有的关于世界通常行为方式的显式可废止知识。我们寻找条件知识库所包含的所有条件断言集合的合理定义。在之前的一篇论文中，克劳斯和作者定义并研究了优先后果关系。他们注意到并非所有优惠关系都可以被视为合理的推理程序。本文研究一类更为严格的后果关系——理性关系。有人认为，任何合理的非单调推理过程都应该定义理性关系。结果表明，理性关系正是可以用排序优先模型或（非标准）概率模型来表示的关系。条件知识库的理性封闭被定义并被证明为标题问题提供了一个有吸引力的答案。证明了该闭包运算的全局性质：它是一个累积运算。它在计算上也是易于处理的。本文假设底层语言是命题式的。
This paper presents a logical approach to nonmonotonic reasoning based on the notion of a nonmonotonic consequence relation. A conditional knowledge base, consisting of a set of conditional assertions of the typeif … then …, represents the explicit defeasible knowledge an agent has about the way the world generally behaves. We look for a plausible definition of the set of all conditional assertions entailed by a conditional knowledge base. In a previous paper, Kraus and the authors defined and studiedpreferentialconsequence relations. They noticed that not all preferential relations could be considered as reasonable inference procedures. This paper studies a more restricted class of consequence relations,rationalrelations. It is argued that any reasonable nonmonotonic inference procedure should define a rational relation. It is shown that the rational relations are exactly those that may be represented by arankedpreferential model, or by a (nonstandard) probabilistic model. The rational closure of a conditional knowledge base is defined and shown to provide an attractive answer to the question of the title. Global properties of this closure operation are proved: it is a cumulative operation. It is also computationally tractable. This paper assumes the underlying language is propositional.