Recursive definitions of predicates are usually interpreted either inductively or coinductively. Recently, a more powerful approach has been proposed, called flexible coinduction, to express a variety of intermediate interpretations, necessary in some cases to get the correct meaning. We provide a detailed formal account of an extension of logic programming supporting flexible coinduction. Syntactically, programs are enriched by coclauses, clauses with a special meaning used to tune the interpretation of predicates. As usual, the declarative semantics can be expressed as a fixed point which, however, is not necessarily the least, nor the greatest one, but is determined by the coclauses. Correspondingly, the operational semantics is a combination of standard SLD resolution and coSLD resolution. We prove that the operational semantics is sound and complete with respect to declarative semantics restricted to finite comodels.

中文翻译：

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灵活的共归纳逻辑编程

谓词的递归定义通常被解释为归纳或共归纳。最近，有人提出了一种更强大的方法，称为灵活共导，来表达各种中间解释，在某些情况下需要得到正确的意思。我们提供了支持灵活共归纳的逻辑编程扩展的详细正式说明。从句法上讲，程序丰富了子句, 具有特殊含义的从句用于调整谓词的解释。像往常一样，声明性语义可以表示为一个固定点，但是，它不一定是最小的，也不一定是最大的，而是由子句决定的。相应地，操作语义是标准SLD解析和coSLD解析的组合。我们证明了操作语义相对于仅限于有限协模型的声明性语义是健全和完整的。