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1.
双析取逻辑程序设计是析取逻辑程序设计的一种扩充,其辩论语框架BDAS为逻辑程序设计中的常识推理提供了一种较为合理的语义框架。 相似文献
2.
析取逻辑程序设计是传统逻辑程序设计最重要的扩充之一,本文通过一些实例说明,现存语义无法充分 表示信息的不完全性。为此,本文提出了双析取逻辑程序设计的概念,我们不仅从句法上将正规则析取逻辑程序推广为双析取逻辑程序。而且建立了一种高度直观,灵活的辩论语义框架BDAS。 相似文献
3.
抽象解释为程序不变式的自动化生成提供了通用的框架,但是该框架下的大多数已有数值抽象域只能表达几何上是凸的约束集.因此,对于包含(所对应的约束集是非凸的)析取语义的特殊程序结构,采用传统数值抽象域会导致分析结果不精确.针对显式和隐式含有析取语义的循环结构,提出了基于循环分解和归纳推理的不变式生成改进方法,缓解了抽象解释分析中出现的语义损失问题.实验结果表明:相比已有方法,该方法能为这种包含析取语义的循环结构生成更加精确的不变式,并且有益于一些安全性质的推理. 相似文献
4.
基于回答集(也称稳定模型)语义的带函数析取逻辑程序是一种重要的知识表示和推理方法。由于判定一个析取逻辑程序是否有回答集是困难的(Σ2完全的),目前还没有有效的方法来计算带函数析取逻辑程序的回答集,主要原因之一是检查一个集合是否是回答集是coNP完全的。提出了带函数析取逻辑程序无基集(unfounded sets)的概念,发现了空无基集(unfounded-free sets)与稳定模型之间的一一对应关系,在此基础上,证明了一个逻辑程序的模型是该程序的稳定模型当且仅当它们对应的一个命题公式是不可满足的,从而在理论上为计算带函数析取逻辑程序的回答集提供了一种有效的途径。 相似文献
5.
在大的数据集合中,开采其中的频繁项目集集合是数据挖掘中极具挑战的重要任务。已经有很多高效的算法被总结了出来。本文提出了一种思想,即开采频繁项目集集合的一 个子集,我们称之为频繁无析取规则集集合,而并非开采完全的频繁项目集集合。我们证明能借助它不读取数据库而还原出频繁项目集集合的全集和它们的支持度。本文还提 提出了一个开采无析取规则集集合的算法HOPE-Ⅱ,实验结果显示了其高效性。我们将它与另一种称为频繁封闭集的精简集进行对比,几乎所有的实验结果都显示使用无析取规则集集合比使用封闭集集合来开采频繁项目集集合更有效。 相似文献
6.
采用逻辑的方法在完备信息系统中展开讨论,通过对公式及公式语义的定义,引出了公式的语义在信息系统上均匀分布的概念。为了对此进行研究,利用Pawlak上近似定义了逻辑公式的粗糙真,其目的就是通过公式的粗糙真对公式语义的均匀分布进行分析。进而,得到了关于粗糙真的相应结论以及如何利用这些结论判定析取特征公式粗糙真的算法。在此基础上,通过信息系统的实例讨论了粗糙真在判定析取特征公式语义均匀分布的具体应用。 相似文献
7.
介绍集值信息系统和区间值信息系统,并提出了同时具有这两种系统特点的区间集值信息系统.依据属性值的语义关系,将区间集值信息系统分为两类:析取(I型)和合取(II型)系统,并对其分别提出了基于优势关系的粗糙集模型,讨论了相关性质.最后用实例分析验证了所提出系统的有效性. 相似文献
8.
集值信息系统是完备信息系统的一种推广,按照语义可划分为合取集值信息系统和析取集值信息系统。属性偏好关系也有两种:属性递增偏好有序和属性递减偏好有序。提出一种新的属性偏好关系,建立了一种新的优势关系。这种优势关系能够表示一类属性偏好既不是递增有序也不是递减有序,而是趋近于某个标准值的情形,称这样的优势关系为属性集中有序,它可应用于某些集值信息系统。 相似文献
9.
根据过程执行的特点,定义了一种以活动为中心的反应式过程元模型,并为其提供了一种图形表示,同时为此元模型指定了一种体现过程运行时行为的动态语义,该语义可表示为一个有限状态自动机.最后举例说明了如何应用它分析过程模型的语义正确性. 相似文献
10.
分析不同的模式集成语义 ,从而得出后处理查询的两种主要运算 :场地间联接和外联接运算 .运用规则把后处理查询先转换成普通表达式 ,再转换成析取条件范式 ,并讨论了其内部树结构的实现机制 ,生成实际用于调度的全局查询超图集 ,并给出了具体的算法 .在此基础上 ,根据超图集的特点 ,给出后处理查询的三级调度 相似文献
11.
In this paper,the relationship between argumentation and closed world reasoning for disjunctive information is studied.In particular,the authors propose a simple and intuitive generalization of the closed world assumption(CWA) for general disjunctive deductive databases(with default negation).This semantics,called DCWA,allows a natural argumentation-based interpretation and can be used to represent reasoning for disjunctive information.We compare DCWA with GCWA and prove that DCWA extends Minker‘s GCWA to the class of disjunctive databases with defacult negation.Also we compare our semantics with some related approaches.In addition,the computational complexity of DCWA is investigated. 相似文献
12.
This paper addresses complexity issues for important problems arising with disjunctive logic programming. In particular, the complexity of deciding whether a disjunctive logic program is consistent is investigated for a variety of well-known semantics, as well as the complexity of deciding whether a propositional formula is satisfied by all models according to a given semantics. We concentrate on finite propositional disjunctive programs with as well as without integrity constraints, i.e., clauses with empty heads; the problems are located in appropriate slots of the polynomial hierarchy. In particular, we show that the consistency check is
2
p
-complete for the disjunctive stable model semantics (in the total as well as partial version), the iterated closed world assumption, and the perfect model semantics, and we show that the inference problem for these semantics is
2
p
-complete; analogous results are derived for the answer sets semantics of extended disjunctive logic programs. Besides, we generalize previously derived complexity results for the generalized closed world assumption and other more sophisticated variants of the closed world assumption. Furthermore, we use the close ties between the logic programming framework and other nonmonotonic formalisms to provide new complexity results for disjunctive default theories and disjunctive autoepistemic literal theories.Parts of the results in this paper appeared in form of an abstract in the Proceedings of the Twelfth ACM SIGACT SIGMOD-SIGART Symposium on Principles of Database Systems (PODS-93), pp. 158–167. Other parts appeared in shortened form in the Proceedings of the International Logic Programming Symposium, Vancouver, October 1993 (ILPS-93), pp. 266–278. MIT Press. 相似文献
13.
The fundamental problem that arises when a ground atom in a disjunctive database is assumed false is discussed. There are basically two different approaches for inferring negative information for disjunctive databases: J. Minker's (1982) generalized closed world assumption (GCWA) and K.A. Ross and R.W. Topor's (1988) disjunctive database rule (DDR). It is argued that neither approach is satisfactory. A database semantics called PWS is proposed. It is shown that for propositional databases with no negative clauses, the problem of determining if a negative ground literal is inferred under the GCWA is co-NP-hard, while the same problem can be solved efficiently under the DDR and PWS. However, in the general case, the problem becomes co-NP-complete for the DDR and PWS. Relationships among GCWA, DDR, and PWS are highlighted. In general, disjunctive clauses are interpreted inclusively under the DDR and unpredictably under the GCWA 相似文献
14.
We present a simple and intuitive extension GCWAG of the generalized closed world assumption (GCWA) from positive disjunctive deductive databases to general disjunctive deductive databases (with default negation). This semantics is defined in terms of unfounded sets and possesses an argumentation-theoretic characterization. We also provide a top-down procedure for GCWAG, which is sound and complete with respect to GCWAG. We investigate two query evaluation methods for GCWAG: database partition, and database splitting. The basic idea of these methods is to divide the original deductive database into several smaller sub-databases and the query evaluation in the original database is transformed into the problem of query evaluation in smaller or simplified components. We prove that these two methods of query evaluation are all sound with respect to GCWAG. 相似文献
15.
Hirofumi Katsuno 《New Generation Computing》1990,8(3):185-209
This paper extends Reiter’s closed world assumption to cases where the assumption is applied in a precedence order between
predicates. The extended assumptions are: thepartial closed world assumption, thehierarchical closed world assumption and thestepwise closed world assumption. The paper also defines an extension of Horn formulas and shows several consistency results about the theory obtained from
the extended Horn formulas by applying the proposed assumptions. In particular, the paper shows that both the hierarchical
closed world assumption and the stepwise closed world assumption characterize the perfect model of stratified programs. 相似文献
16.
José Alberto Fernández Jorge Lobo Jack Minker V. S. Subrahmanian 《Annals of Mathematics and Artificial Intelligence》1993,8(3-4):449-474
We show that stable models of logic programs may be viewed as minimal models of programs that satisfy certain additional constraints. To do so, we transform the normal programs into disjunctive logic programs and sets of integrity constraints. We show that the stable models of the normal program coincide with the minimal models of the disjunctive program thatsatisfy the integrity constraints. As a consequence, the stable model semantics can be characterized using theextended generalized closed world assumption for disjunctive logic programs. Using this result, we develop a bottomup algorithm for function-free logic programs to find all stable models of a normal program by computing the perfect models of a disjunctive stratified logic program and checking them for consistency with the integrity constraints. The integrity constraints provide a rationale as to why some normal logic programs have no stable models. 相似文献
17.
Disjunctive minimal generators were proposed by Zhao, Zaki, and Ramakrishnan (2006). They defined disjunctive closed itemsets and disjunctive minimal generators through the disjunctive support function. We prove that the disjunctive support function is compatible with the closure operator presented by Zhao et al. (2006). Such compatibility allows us to adapt the original version of the Titanic algorithm, proposed by Stumme, Taouil, Bastide, Pasquier, and Lakhal (2002) to mine iceberg concept lattices and closed itemsets, to mine disjunctive minimal generators. We present TitanicOR, a new breadth-first algorithm for mining disjunctive minimal generators. We evaluate the performance of our method with both synthetic and real data sets and compare TitanicOR’s performance with the performance of BLOSOM (Zhao et al., 2006), the state of the art method and sole algorithm available prior to TitanicOR for mining disjunctive minimal generators. We show that TitanicOR’s breadth-first approach is up to two orders of magnitude faster than BLOSOM’s depth-first approach. 相似文献
18.
19.
Michael Gelfond 《Annals of Mathematics and Artificial Intelligence》1994,12(1-2):89-116
The purpose of this paper is to expand the syntax and semantics of logic programs and disjunctive databases to allow for the correct representation of incomplete information in the presence of multiple extensions. The language of logic programs with classical negation, epistemic disjunction, and negation by failure is further expanded by new modal operators K and M (where for the set of rulesT and formulaF, KF stands for F is known to be true by a reasoner with a set of premisesT and MF means F may be believed to be true by the same reasoner). Sets of rules in the extended language will be called epistemic specifications. We will define the semantics of epistemic specifications (which expands the semantics of disjunctive databases from) and demonstrate their applicability to formalization of various forms of commonsense reasoning. In particular, we suggest a new formalization of the closed world assumption which seems to better correspond to the assumption's intuitive meaning. 相似文献
20.
《IEEE transactions on pattern analysis and machine intelligence》1985,(7):620-633
In this paper we consider approaches to updating databases containing null values and incomplete information. Our approach distinguishes between modeling incompletely known worlds and modeling changes in these worlds. As an alternative to the open and closed world assumptions, we propose the expanded closed world assumption. Under this assumption, we discuss how to perform updates on databases containing set nulls, marked nulls, and simple conditional tuples, and address some issues of refining incompletely specified information. 相似文献