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arXiv cs/0103008cs.LOcs.PL
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Horn逻辑程序的极限

The Limits of Horn Logic Programs

Shilong Ma, Yuefei Sui, Ke Xu

摘要:

给定Horn逻辑程序序列$\{Π_n\}$,$\{Π_n\}$的极限$Π$是这样的子句集合,使得$Π$中的每个子句属于几乎每个$Π_n$,并且无限多个$Π_n$中的每个子句也属于$Π$.极限程序$Π$仍然是Horn,但可能是无限的。本文考虑给定Horn逻辑程序序列$\{Π_n\}$的极限的最小Herbrand模型是否等于每个逻辑程序$Π_n$的最小Herbrand模型的极限。本文证明了这一性质一般不成立,但如果Horn逻辑程序满足一个可语法检验且可由一类Horn逻辑程序满足的假设,则这一性质成立。因此,在此假设下,我们可以通过每个有限程序$Π_n$的最小Herbrand模型序列来逼近极限$Π$的最小Herbrand模型.我们还证明了,如果一个有限Horn逻辑程序满足这个假设,那么这个程序的最小Herbrand模型是递归的。最后,利用动力系统的稳定性概念,证明了这一假设是保证Horn逻辑程序不动点稳定的充分条件。

英文摘要:

Given a sequence $\{Π_n\}$ of Horn logic programs, the limit $Π$ of $\{Π_n\}$ is the set of the clauses such that every clause in $Π$ belongs to almost every $Π_n$ and every clause in infinitely many $Π_n$'s belongs to $Π$ also. The limit program $Π$ is still Horn but may be infinite. In this paper, we consider if the least Herbrand model of the limit of a given Horn logic program sequence $\{Π_n\}$ equals the limit of the least Herbrand models of each logic program $Π_n$. It is proved that this property is not true in general but holds if Horn logic programs satisfy an assumption which can be syntactically checked and be satisfied by a class of Horn logic programs. Thus, under this assumption we can approach the least Herbrand model of the limit $Π$ by the sequence of the least Herbrand models of each finite program $Π_n$. We also prove that if a finite Horn logic program satisfies this assumption, then the least Herbrand model of this program is recursive. Finally, by use of the concept of stability from dynamical systems, we prove that this assumption is exactly a sufficient condition to guarantee the stability of fixed points for Horn logic programs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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