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arXiv cs/0509024cs.LO
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具有聚集的逻辑程序的良基稳定语义

Well-founded and Stable Semantics of Logic Programs with Aggregates

Nikolay Pelov, Marc Denecker, Maurice Bruynooghe

摘要:

在本文中,我们提出了一个框架的语义和计算的逻辑编程的上下文中的聚合。在我们的研究中,聚合可以是任意解释的二阶谓词或函数。我们定义扩展的Kripke-Kleene,良好的基础和稳定的语义聚合程序。语义是基于一个三值的直接后果算子的概念的聚合程序。这种算子近似于程序的标准二值直接后果算子,并诱导出唯一的Kripke-Kleene模型,唯一的良基模型和稳定模型的集合。我们研究不同的方式来定义这样的运营商,从而获得一个框架的语义,提供不同的权衡精度和易处理性。特别是,我们调查的操作,保证这三种类型的语义的计算保持在同一水平上的逻辑程序没有聚集的条件。其他结果表明,在实践中,即使是有效的三值直接后果运营商,这是非常低的精度等级,仍然提供最佳精度。

英文摘要:

In this paper, we present a framework for the semantics and the computation of aggregates in the context of logic programming. In our study, an aggregate can be an arbitrary interpreted second order predicate or function. We define extensions of the Kripke-Kleene, the well-founded and the stable semantics for aggregate programs. The semantics is based on the concept of a three-valued immediate consequence operator of an aggregate program. Such an operator approximates the standard two-valued immediate consequence operator of the program, and induces a unique Kripke-Kleene model, a unique well-founded model and a collection of stable models. We study different ways of defining such operators and thus obtain a framework of semantics, offering different trade-offs between precision and tractability. In particular, we investigate conditions on the operator that guarantee that the computation of the three types of semantics remains on the same level as for logic programs without aggregates. Other results show that, in practice, even efficient three-valued immediate consequence operators which are very low in the precision hierarchy, still provide optimal precision.

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