HBase的时态语义处理机制和时态查询语言

国家自然科学基金项目HBase(Historicl Data and Knowledge Base System)是一个处理历史性数据与知识的数据库系统,它拥有基本的时态查询操作。本文介绍了在关系数据模型基础上增加时态语义而得到的HBase数据结构,并讨论它的时态查询语言HBASE/T的主要技术,如:WHEN子句,时态函数、区间比较、时态查询等。     

时态粗糙神经网

论文提出了一种基于粗糙集和时态概念的新神经网模型—时态粗糙神经网。在神经网的输入中加入时间的因素,即神经网络的输入是时间的函数,从而把传统的神经元改造成了时态神经元;时态粗糙神经网中的神经元是时态粗糙神经元,它包括一对时态神经元,即将数据中的上边界和下边界加入时间因素以后,作为神经网络的输入和输出。当网络的输入和输出不是单值数据而是一个随时间变化的数据的集合时,经典的神经网络建立的预测模型的输出就会产生较大的误差,而基于时态粗糙理论的神经网络则可以很好地解决这个问题,更能真实刻画实际问题。从而为解决这类问题提供了一个较好的理论模型。     

多时间粒度下时态数据库设计中时态类型的处理

在许多大型信息系统中需要存储大量的历史数据．为了有效地组织这些时间变化数据，可以使用时态函数依赖（TFDs）对时态数据库进行有效地设计．由于多时间粒度的使用，数据库设计算法需要在计算机上实现表示时态类型间的关系的逻辑结构和时态类型间的相关操作．为此提出了细于关系矩阵和封闭的时态类型集，并且对于给定的时态类型集及其细于关系矩阵，给出了一个自动生成它的一个封闭集及封闭集对应的细于关系矩阵的有效算法，通过提出的细于关系矩阵和封闭集算法，可以方便地在计算机上实现时态数据库设计算法需要的时态类型间的细于关系比较和glb操作。     

基于不确定信息的时态索引技术

扩展了时态数据库中时态信息的表示方法，使它能处理不确定时态信息。并实现相应索引机制，从而为支持不确定时态信息的时态数据库打下基础。性能测试的结果说明，该索引不但在功能上支持不确定时态数据，而且在性能上也优于已有的时态索引技术。     

时态空间查询语言及时态空间GIS结构模型

时态空间数据一体化是实现地理信息共享与发布的基础，在总结相关领域研究状况的基础上，对时态空间数据库在地理信息系统上的实现进行了一些探讨，设计了一种混合式时态空间查询语言，并以此语言为基础，构建了时态空间地理信息系统结构模型。     

TempDB:时态数据管理系统

为了适应时态数据库发展需求,针对目前时态数据库技术实现则相对滞后现状,设计和实现了时态数据处理原型系统TempDB. TempDB采用中间件的架构实现,使用具有代表性的时态查询语言--ATSQL2,将时态操作语言转换成与之语义等价的、标准的SQL语言,然后在后台DBMS上执行,实现了基本的时态数据管理功能. TempDB总结应用了相关理论知识,同时也为时态数据库系统的产品化积累了经验.     

基于XPath数据模型的双时态扩展

XML作为Web上新的数据发布语言,将成为Web下一代"数据表达"和"数据交换"的统一标准.然而XML文档很少是静止的,它经常会被修改,引入"时态表达"后时态XML文档能够记录一系列的修改痕迹,提供了一种高效可行的XML版本管理方案.另一方面XML表达时态信息比关系模型更自然,时态数据库的研究人员开始将部分焦点转向研究如何利用XML实现时态信息处理.提出了一个双时态XML数据模型并给出了形式化定义,该模型将一个双时态XML文档建模成一个带有"双时态元素"边标记的有向树形图.还讨论了该模型映射到双时态XML文档的两种映射方法;并采用扩展DOM API的方法实现了模型以及映射.最后通过实验对比了扩展DOM实现模型和不扩展DOM实现模型两种实现方法,两种模型映射到双时态XML文档的映射方法.     

不确定时态信息表示及时态运算的扩展

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。     

基于Hadoop的时态信息存储与时态关系演算问题研究

面对海量的非结构化时态信息,构建了在分布式环境下的数据存储模型,并在此基础上提出一种基本的时态数据处理方法。使用Hadoop平台下的分布式、非结构化数据库HBase对海量时态数据进行存储,构造以时态集合为时态存储单元的时态数据存储模型;针对分布式处理特征和时态集合数据类型,提出一种在Map/Reduce编程计算模式下进行海量时态信息关系演算的实现方法;通过扩展时态区间关系运算,实现以时态集合为基本时态数据操作对象的交、并等关系运算。以医疗时态数据作为研究实例,表明了所提出的时态数据存储模型和关系演算方案在分布式应用系统下的适用性。     

时态查询语言对处理不明确时间间隔的扩展

关于时态数据库的先前工作,主要是建立在时态属性的时间间隔和事件的开始/终止点都十分清楚的基础上.然而,在许多实际情况中,事件的时间界限并不十分清楚.因此,表示不明确时间,并给出处理不明确时间查询的方法,是对时态数据库中目前仍缺少的一个有效的扩展.讨论了时态数据库处理不明确时间存在的一些问题,并描述不明确时间间隔的方法.之后扩展了各种时态运算,并给出了与不明确时间相关的新运算符.也提出了能够处理不明确时间的查询语言扩展.在此讨论的时态查询语言对处理不明确时间间隔的扩展和丰富时态数据库的适应性有一定作用.     

Modal Logic over Finite Structures

We investigate properties of propositional modal logic over the classof finite structures. In particular, we show that certain knownpreservation theorems remain true over this class. We prove that aclass of finite models is defined by a first-order sentence and closedunder bisimulations if and only if it is definable by a modal formula.We also prove that a class of finite models defined by a modal formulais closed under extensions if and only if it is defined by a -modal formula.     

Control sets on grammars using depth-first derivations

Control sets on grammars are extended to depth-first derivations. It is proved that a context-free language is generated by the depth-first derivations of an arbitrary context-free grammar controlled by an arbitrary regular set. This result is sharpened to obtain a new characterization of the family of derivation-bounded languages: a languageL is derivation bounded if and only if it is generated by the depth-first derivations of a context-free grammarG controlled by a regular subsetR of the Szilard language ofG. The left-derivation-bounded languages are characterized analogously using leftmost derivations. It is proved that a grammarG is nonterminal bounded if and only if the Szilard language defined using only the depth-first derivations ofG is regular. Finally, it is proved that if a family of languagesC is a trio, a semi-AFL, an AFL, or an AFL closed under -free substitution, then the family of languages generated using arbitrary context-free grammars controlled by members ofC is full, is closed under reversal, and has the closure properties assumed ofC.     

On lattices of regular sets of natural integers closed under decrementation

We consider lattices of regular sets of non negative integers, i.e. of sets definable in Presburger arithmetic. We prove that if such a lattice is closed under decrement then it is also closed under many other functions: quotients by an integer, roots, etc. We characterize the family of such functions.     

正规树文法的产生式相交判定

在针对产生式不相交的正规树文法的XML类型检查中,需要对正规树文法的产生式进行相交判定.基于正规树文法的产生式的构成特点,提出了基于自动机的相交判定算法.根据产生式的内容模型即正则表达式,构建相应自动机,判定两个自动机的交是否为空,该算法的时间复杂度为O( ‖ E1‖·‖ E2‖·|∑E1 ∪∑E2 |).实验结果表明,该算法运行正确且高效,可以应用到针对产生式不相交的正规树文法的XML类型检查中.     

Designing A Disjoint Paths Interconnection Network with Fault Tolerance and Collision Solving

In fault-tolerant interconnection designs, many prior researches suggest good use of disjoint paths to improve the reliability of interconnection networks. Although disjoint paths increase reliability, they always cost the throughput penalty. To address the problems of both performance and fault-tolerant capability, the following issues should be carefully considered: (1) guarantee of at least two disjoint paths, (2) easy rerouting between disjoint paths, (3) keep low rerouting hops, (4) solve the occurrences of packets’ collision. In this paper, we consider these issues to design a fault-tolerant network called CSMIN (Combining Switches Multistage Interconnection Network). CSMIN provides two disjoint paths to guarantee one fault-tolerant and can dynamically reroute packets between these two paths to solve the collision situation. In other words, to switch packets between these two disjoint paths easily, CSMIN causes these two disjoint paths to have regular distances at each stage. Accordingly, a packet can be dynamically sent to the other disjoint path if it encounters a faulty or busy element. In addition, CSMIN presents low rerouting hops (an average of one rerouting hop) to maintain a low collision ratio. From the simulation result, CSMIN performs with a better arrival ratio than Gamma and other related disjoint paths networks do.This research was supported by the National Science Council NSC-91-2218-E-324-006.     

Homotopic Morphing of Planar Curves

This paper presents an algorithm for morphing between closed, planar piecewise‐C¹ curves. The morph is guaranteed to be a regular homotopy, meaning that pinching will not occur in the intermediate curves. The algorithm is based on a novel convex characterization of the space of regular closed curves and a suitable symmetric length‐deviation energy. The intermediate curves constructed by the morphing algorithm are guaranteed to be regular due to the convexity and feasibility of the problem. We show that our method compares favorably with standard curve morphing techniques, and that these methods sometimes fail to produce a regular homotopy, and as a result produce an undesirable morph. We explore several applications and extensions of our approach, including morphing networks of curves with simple connectivity, morphing of curves with different turning numbers with minimal pinching, convex combination of several curves, and homotopic morphing of b‐spline curves via their control polygon.     

Homomorphism preservation on quasi-wide classes

A class of structures is said to have the homomorphism preservation property just in case every first-order formula that is preserved by homomorphisms on this class is equivalent to an existential-positive formula. It is known by a result of Rossman that the class of finite structures has this property and by previous work of Atserias et al. that various of its subclasses do. We extend the latter results by introducing the notion of a quasi-wide class and showing that any quasi-wide class that is closed under taking substructures and disjoint unions has the homomorphism preservation property. We show, in particular, that classes of structures of bounded expansion and classes that locally exclude minors are quasi-wide. We also construct an example of a class of finite structures which is closed under substructures and disjoint unions but does not admit the homomorphism preservation property.     

基于C2C的电子商务信用体系研究

Credit problem is the main bottleneck which hinders the development of e-commerce. This paper analyzes the current representative C2C credit evaluation models of Taobao and Youa, and proposes an improved model. The improved model uses a multi-standard evaluation system and new credit rating rules. And the evaluation algorithm considers the score of multi-standards, category and price of the commodity together, using a weighted system to calculate the credit score then to determine the credit rating. It solves the main problems which the current C2C credit rating algorithms haven't settled. In addition, the model puts forward some identification measures of false trading, the ID verification rules, and a third-party credit certification center, which partly solve the credit fraud problems arising from the credit island and credit speculation. Finally, the paper compares the improved model with current models to show its superiority.     

Vectorial languages and linear temporal logic

Determining for a given deterministic complete automaton the sequence of visited states while reading a given word is the core of important problems with automata-based solutions, such as approximate string matching. The main difficulty is to do this computation efficiently. Considering words as vectors and working on them using vectorial operations allows to solve the problem faster than using local operations.

In this paper, we show first that the set of vectorial operations needed by an algorithm representing a given automaton depends on the language accepted by the automaton. We give precise characterizations for star-free, solvable and regular languages using vectorial algorithms. We also study classes of languages associated with restricted sets of vectorial operations and relate them with languages defined by fragments of linear temporal logic.

Finally, we consider the converse problem of constructing an automaton from a given vectorial algorithm. As a byproduct, we show that the satisfiability problem for some extensions of LTL characterizing solvable and regular languages is PSPACE-complete.     

Combining Nonstably Infinite Theories

The Nelson–Oppen combination method combines decision procedures for first-order theories over disjoint signatures into a single decision procedure for the union theory. In order to be correct, the method requires that the component theories be stably infinite. This restriction makes the method inapplicable to many interesting theories such as, for instance, theories having only finite models. In this paper, we describe two extensions of the Nelson–Oppen method that address the problem of combining theories that are not stably infinite. In our extensions, the component decision procedures exchange not only equalities between shared variables but also certain cardinality constraints. Applications of our results include the combination of theories having only finite models, as well as the combination of nonstably infinite theories with the theory of equality, the theories of total and partial orders, and the theory of lattices with maximum and minimum. Calogero G. Zarba: Work done by this author at Stanford University and later at LORIA and INRIA-Lorraine.