共查询到19条相似文献,搜索用时 46 毫秒
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叶小平 《计算机研究与发展》2007,44(11):1971-1979
时态数据处理多是基于关系数据库平台,时态数据库模型也以时态关系数据模型为主.关系数据模型难以处理具有复杂类型的数据对象,而面向对象数据模型还缺乏商业化应用平台.现有关系数据库平台大多增加了面向对象基本功能,形成了对象关系数据库系统,因此将对象关系数据模型进行时态扩充就显得十分必要和具有可行性.首先在现有时态关系数据模型基础上,提出了一种基于对象关系双时态数据模型,而这种数据模型适合于在现有数据库平台上实现;其次,在该模型框架内,讨论了时态对象关系模式与时态关系模式相互间的联系与转换,这也是由时态关系扩充到对象关系的基本要求;再次,分析了时态模型中时态变量复杂语义和相应绑定算法,这是时态数据库能够有效运行的基本课题之一;最后,研究了基于时态变量复杂语义的时态对象关系数据操作代数,从而为时态对象关系模式的查询进行了必要的理论探讨. 相似文献
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基于BCDM的含有变量的双时态关系代数研究* 总被引:2,自引:0,他引:2
在BCDM(双时态概念数据模型)中,时间变元Now和UC的存在解决了时态记录的频繁更新问题;但是时态变元的存在又给数据库的操作带来某种不确定性甚至是错误,同时引起关系代数运算的歧义。基于BCDM,通过绑定时间变元,用时态映射的集合定义时态关系,由此建立了一种含有时间变元的双时态关系代数体系。该关系代数体系在双时态运算下是封闭的。 相似文献
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不确定时态的语义处理及近似运算是时态系统的研究与应用中不可忽视的基本问题.不确定语义的转换、时态粒度的规范化以及不确定时态间的近似运算和语义还原成为不确定时态信息处理中的难点.针对时态跨度中不确定语义造成的时态不确定性与多样性,提出了对不确定语义进行转换的思想,将其转换为区间数的形式,结合时态的粒度属性,给出了不确定时态跨度的形式化描述,使其成为可计算问题;根据时态粒度约束对不确定时态跨度进行了规范化处理,使其可以参与运算;最后结合时态区间数给出了不确定时态跨度间的运算及语义还原方法,有效地处理了不确定时态跨度间的复杂运算,典型的运算过程均给出了示例予以说明. 相似文献
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现实世界的信息是和时间紧密相关的,因而记录和处理信息的数据库系统应该对时态问题进行考虑,以便更有效地解决现实问题;另一方面,现实世界的某些属性又很难用属性值简单描述。首先是用Rough理论对属性值进行一种刻画,用二元数组来表达属性值,并且将这种属性值的表达方式推广到一般情形,而后从时态映射的观点描述时态元组和时态关系,并由此形式描述相应的时态关系运算,从而建立了一套时态关系代数体系。 相似文献
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模糊时态数据库关系代数演算规则分析 总被引:1,自引:0,他引:1
为了解决时态数据库对客观世界更符合实际抽象描述,能有效表示和处理复杂对象的模糊时态特性,从基本模糊时态数据模型入手,定义了一系列模糊时态关系操作元素,并论证了模糊时态区间关系代数的语法和语义,建立了一个能描述模糊时态信息的关系代数理论体系.避免了时态数据库不能提供表达模糊时态信息的环境设施,也增强了现有的时态数据库描述模糊事物特性的能力. 相似文献
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不确定时态信息表示及时态运算的扩展 总被引:1,自引:0,他引:1
时态信息表示和查询是时态数据库的研究重点,但现有的时态数据库模型在处理不确定时态信息方面仍存在较大困难。而现实生活中很多时态信息都是不确定的,故提出了一种不确定时态信息的表示方法,并扩展时态运算使其支持不确定时态信息的处理和查询,从而扩展了时态数据库的适用范围。 相似文献
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基于BCDM的双时态关系代数 总被引:10,自引:0,他引:10
双时态概念数据模型BCDM是一种重要的时态数据库模型,基于BCDM模型,建立了一种双时态关系代数.首先,对时态数据库事务时间和有效时间进行规范化的定义,给出BCDM中时间元素的规范化定义和演算描述;而后,定义时态映射,用以描述BCDM中的双时态元组,并形式描述时态映射的演算;最后,用时态映射定义的元组对双时态关系进行定义,并由此给出双时态关系代数运算的形式化描述. 相似文献
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Similarity of Legal Cases: From Temporal Relations of Affairs 总被引:1,自引:0,他引:1
Case-based reasoning has played an important role in legal reasoning systems. As one criteria for similarity of cases, temporal relationsamong affairs in legal cases should be compared. Thus far in many legalreasoning systems, cases have been described as sequences of pointwiseevents, or at best, simple time intervals, and they have been related bypredicates such as before, after, while,and so on. However, such relations may depend on each implementer'spersonal view, and also require much labor to write down by hand. In this paper, we first propose a classification of affair types by their temporal features, and according to those types, we propose several assumption rules that prescribe the temporal relations between affair types. The temporal relations are automatically generated by these rules. Thereafter, we discuss how thesetemporal relations work in the comparison of similarity of cases. Inthe process of comparison, inadequate temporal relations need to beamended. For this purpose, we introduce revision rules, that refute theresults of assumption rules. 相似文献
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使用扩展的持续时间演算(EDC)模型,给出了时间化的RAISE描述语言(RSL)的一个子集的指称语义.在扩展的持续时间演算模型中加入了一些新的特征,并探究了它们的代数定律.这些定律在形式化实时程序和验证实时性质中起着重要作用.最后还给出了时间化RSL的一些代数定律.这些定律可以从其指称语义证明,并用于程序的转化和优化. 相似文献
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M.A. Cárdenas Viedma R. Marín Morales 《Annals of Mathematics and Artificial Intelligence》2002,36(4):357-380
In this paper we establish the relationship between the syntax and semantics of a fuzzy temporal constraint logic (FTCL) proposed by Cárdenas et al. FTCL enables us to express interrelated events by means of fuzzy temporal constraints. Moreover, it provides a resolution principle for performing inferences which take these constraints into account. FTCL is compatible with the theoretical temporal reasoning model proposed by Marín et al. – the Fuzzy Temporal Constraint Networks (FTCN). The main contributions of this paper are, on the one hand, the proofs of the FTCL-deduction and the FTCL-refutation theorems, and, on the other, the proof of the soundness of the refutation by resolution in this formal system, together with an exhaustive study of its completeness. 相似文献
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UML活动图的时序逻辑语义 总被引:10,自引:1,他引:10
UML活动图可以表示不同抽象级的控制流,很适合用于对系统的行为建模.但是缺乏精确的语义使得难以对它所表示的系统行为进行分析.XYZ/E是一可执行线性时序逻辑语言,既可描述系统的动态行为又可表示程序性质,用它对活动图形式化后,就可在统一的逻辑框架下分析活动图的性质.定义了一个有向图结构用以表示UML活动图,再给出其XYZ/E语义,并用一个例子说明活动图到XYZ/E的语义转换,为进一步的分析提供形式化基础. 相似文献
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区域连接演算(RCC)是定性空间推理的重要基础理论之一.但由于缺乏必要的度量,RCC只是粗略地描述空间拓扑关系而难以对其更准确地描述,也难以利用RCC描述除拓扑关系之外的其它空间关系,如距离、方向等.本文在RCC理论的基础上,提出了区域伸缩演算(RESC).RESC增加了一个全等CG的原始空间关系,引入了两个新颖的对区域的演算函数,即区域延伸和区域收缩,从而给出了一种以区域为单位的形式化的度量方法.利用RESC,不仅可以扩展RCC-8拓扑关系,而且能以灵活多样的粒度来描述区域间的距离关系、方向关系、位置关系以及运动关系.RESC增强了RCC的空间关系表示能力,拓展了RCC理论的适用范围. 相似文献
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Temporal logic can be used to describe processes: their behaviour ischaracterized by a set of temporal models axiomatized by a temporaltheory. Two types of models are most often used for this purpose: linearand branching time models. In this paper a third approach, based onsocalled joint closure models, is studied using models which incorporateall possible behaviour in one model. Relations between this approach andthe other two are studied. In order to define constructions needed torelate branching time models, appropriate algebraic notions are defined(in a category theoretical manner) and exploited. In particular, thenotion of joint closure is used to construct one model subsuming a setof models. Using this universal algebraic construction we show that aset of linear models can be merged to a unique branching time model.Logical properties of the described algebraic constructions are studied.The proposed approach has been successfully aplied to obtain anappropriate semantics for non-monotonic reasoning processes based ondefault logic. References are discussed that show the details of theseapplications. 相似文献
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Steven Givant 《Journal of Automated Reasoning》2006,37(4):277-322
A variable-free, equational logic $\mathcal{L}^\timesA variable-free, equational logic based on the calculus of relations (a theory of binary relations developed by De Morgan, Peirce, and Schr?der during the
period 1864–1895) is shown to provide an adequate framework for the development of all of mathematics. The expressive and
deductive powers of are equivalent to those of a system of first-order logic with just three variables. Therefore, three-variable first-order
logic also provides an adequate framework for mathematics. Finally, it is shown that a variant of may be viewed as a subsystem of sentential logic. Hence, there are subsystems of sentential logic that are adequate to the
task of formalizing mathematics.
This paper is an expanded version of a talk given by the author at the Special Session on Automated Reasoning in Mathematics
and Logic, held March 8–10, 2002, at the Georgia Institute of Technology, during the Joint Southeastern Section MAA/Southeast
Regional AMS Meeting. The session was organized by Johan G. F. Belinfante. 相似文献