Enabling flexible queries with guarantees in P2P systems

The Squid peer-to-peer information discovery system supports flexible queries using partial keywords, wildcards, and ranges. It is built on a structured overlay and uses data lookup protocols to guarantee that all existing data elements that match a query are found efficiently. Its main innovation is a dimension-reducing indexing scheme that effectively maps multidimensional information space to physical peers.     

RPES:一种新的多维数据可视化方法

当前,面对科学、工程和商业领域中海量的多维数据,用户迫切需要使用有效的可视化工具在知识发现、信息认知及信息决策过程中对其进行理解。针对传统基于降维映射的数据可视化方法计算复杂度高且无法提供维度分布信息的缺点,提出一种基于正2k边形的多维数据可视化方法RPES,通过建立多维数据空间的低维"参照物"——正2k边形坐标系,以减小多维对象在正2k边形坐标系及多维数据空间中的坐标差别为准则,使用最优化方法对其进行降维,以点云的形式标绘在低维可视空间中,完成多维数据的降维可视展现。实验证明,RPES的降维算法高效、容易实现,适用于数据量较大、维度较高的数据集,可视化结果不仅易于理解,而且能够有效提供维度分布信息,有利于用户发掘隐性知识,辅助其进行基于多维数据的决策。     

A Novel Approach for Information Discovery in Wireless Sensor Grids

Multi-dimensional Wireless sensor grids (WSG)s are deployed in complex environments to sense and collect data relating to multiple attributes (multi-dimensional data). Such networks present unique challenges to data dissemination, data storage of in-network information discovery. However, in order to fully exploit these networks for mission-critical applications, energy-efficient and scalable solutions for information discovery are essential. In this paper, we propose a novel and adaptive method for information discovery for multi-dimensional WSGs that can significantly increase network lifetime and minimize query processing latency, resulting in quality of service improvements that are of immense benefit to mission-critical applications. Further, we investigate efficient strategies for information discovery in large-scale wireless sensor networks and propose the Adaptive Multi-Dimensional Multi-Resolution Architecture (A-MDMRA) that efficiently combines “push” and “pull” strategies for information discovery. The A-MDMRA also adapts to variations in the frequencies of events and queries in the network to construct optimal routing structures. We present simulation results to show that the proposed approach to information discovery offers significant improvements on query resolution latency compared with current approaches. We observe that our proposed methods outperform existing schemes such as double rulings, comb needle and Time-Parameterized Data Centric Storage by up to 14% in terms of query resolution latency and up to 20% in terms of energy-efficiency.     

基于结构化对等网的分布式资源发现方法

为了解决大型分布式系统由集中管理导致的扩展性和鲁棒性差的问题,利用改进的结构化对等网组织分布式计算资源,将逻辑空间中的节点分为主机节点和资源节点,分别采取相容性Hash和位置保留Hash与对等网逻辑空间匹配,以满足资源信息的范围查询。     

A Self-Organized Grouping (SOG) Framework for Efficient Grid Resource Discovery

Dynamic and heterogeneous characteristics of large-scale Grids make the fundamental problem of resource discovery a great challenge. This paper presents a self-organized grouping (SOG) framework that achieves efficient Grid resource discovery by forming and maintaining autonomous resource groups. Each group dynamically aggregates a set of resources together with respect to similarity metrics of resource characteristics. The SOG framework takes advantage of the strengths of both centralized and decentralized approaches that were previously developed for Grid/P2P resource discovery. The design of SOG minimizes the overhead incurred by the process of group formation and maximizes the performance of resource discovery. The way SOG approach handles resource discovery queries is metaphorically similar to searching for a word in an English dictionary, by identifying its alphabetical group at the first place, and then performing a lexical search within the group. Because multi-attribute range queries represent an important aspect of resource discovery, we devise a generalized approach using a space-filling curve in conjunction with the SOG framework. We exploit the Hilbert space-filling curve’s locality preserving and dimension reducing mapping. This mapping provides a 1-dimensional grouping attribute to be used by the SOG framework. Experiments show that the SOG framework achieves superior look-up performance that is more scalable, stable and efficient than other existing approaches. Furthermore, our experimental results indicate that the SOG framework has little dependence on factors such as resource density, query type, and Grid size.     

完备鉴别保局投影人脸识别算法

为了充分利用保局总体散布主元空间内的鉴别信息进行人脸识别,提出了一种完备鉴别保局投影(complete discriminant locality preserving projections,简称CDLPP)人脸识别算法.鉴于Fisher鉴别分析和保局投影已经被广泛的应用于人脸识别,完备鉴别保局投影(locality preserving projections,简称LPP)算法将这两者结合起来,分析了保局类内散布、类间散布和总体散布的主元空间和零空间内包含的鉴别信息.该算法采用奇异值分解(singular value decomposition,简称SVD),去除了不含任何鉴别信息的保局总体散布的零空间;分别在保局类内散布的主元空间和零空间提取规则鉴别特征和不规则鉴别特征;用串联的方式在特征层融合规则鉴别特征和不规则鉴别特征形成完备的鉴别特征进行人脸识别.在ORL库、FERET子库和PIE子库上的大量识别实验充分表明了完备鉴别保局投影算法的性能优于线性鉴别分析、保局投影和鉴别保局投影等现有的子空间人脸识别算法,验证了算法的有 效性.     

Exploration of Ordinal Data Using Association Rules

The discovery of association rules is a very efficient data mining technique that is especially suitable for large amounts of categorical data. This paper shows how the discovery of association rules can be of benefit for numeric data as well. Based on a review of previous approaches we introduce Q2, a faster algorithm for the discovery of multi-dimensional association rules over ordinal data. We experimentally compare the new algorithm with the previous approach, obtaining performance improvements of more than an order of magnitude on supermarket data. In addition, a new absolute measure for the interestingness of quantitative association rules is introduced. It is based on the view that quantitative association rules have to be interpreted with respect to their Boolean generalizations. This measure has two major benefits compared to the previously used relative interestingness measure; first, it speeds up rule extraction and evaluation and second, it is easier to interpret for a user. Finally we introduce a rule browser which supports the exploration of ordinal data with quantitative association rules.     

使用LVS 和Squid 构建代理服务器集群系统

LVS是优秀的集群及IP负载均衡开源软件,同样Squid是目前最通用的开源代理服务系统软件．本文讲述如何利用LVS和Squid构建高效可靠的代理服务器集群系统．     

基于U-tree的不确定移动对象索引策略

通过在U-tree中添加时间戳和速度矢量等时空因素,提出一种基于U-tree的高效率当前及未来不确定位置信息检索的索引结构TPU-tree,可以支持多维空间中不确定移动对象的索引,并提出了一种改进的基于p-bound的MP_BBRQ(modifiedp-bound based range query)域查询处理算法,能够引入搜索区域进行预裁剪以减少查询精炼阶段所需代价偏高的积分计算.实验仿真表明,采用MP_BBRQ算法的TPU-tree概率查询性能极大地优于传统的TPR-tree索引,且更新性能与传统索引大致相当,具有良好的实用价值.     

A Visual Formalism for Computational Tree Logic

The recent advances in computer graphics and multimedia technology provide new means for the visualization of abstract information spaces through the use of multi-dimensional and multi-modal communication channels. In the context of computer-aided verification, this potential can be effectively employed to provide visual notations for mathematical formalisms. We describe a visual system which supports visual presentation and manipulation of temporal sequencing properties expressed in the formalism of computation tree logic. The system enforces a metaphoric transposition of the abstract temporal semantics of the logic onto a concrete visual space through the use of 3D graphics, multiple windowing, color associations, and through the joint and coherent exploitation of both textual and graphic representations. This results in a complex interaction environment supporting syntactic parsing, semantic understanding, and visual editing of temporal expressions.     

HD Tree: A novel data structure to support multi-dimensional range query for P2P networks

There are two basic concerns for supporting multi-dimensional range query in P2P overlay networks. The first is to preserve data locality in the process of data space partitioning, and the second is the maintenance of data locality among data ranges with an exponentially expanding and extending rate. The first problem has been well addressed by using recursive decomposition schemes, such as Quad-tree, K-d tree, Z-order, and Hilbert curve. On the other hand, the second problem has been recently identified by our novel data structure: HD Tree. In this paper, we explore how data locality can be easily maintained, and how range query can be efficiently supported in HD Tree. This is done by introducing two basic routing strategies: hierarchical routing and distributed routing. Although hierarchical routing can be applied to any two nodes in the P2P system, it generates high volume traffic toward nodes near the root, and has very limited options to cope with node failure. On the other hand, distributed routing concerns source and destination pairs only at the same depth, but traffic load is bound to some nodes at two neighboring depths, and multiple options can be found to redirect a routing request. Because HD Tree supports multiple routes between any two nodes in the P2P system, routing in HD Tree is very flexible; it can be designed for many purposes, like fault tolerance, or dynamic load balancing. Distributed routing oriented combined routing (DROCR) algorithm is one such routing strategy implemented so far. It is a hybrid algorithm combining advantages from both hierarchical routing and distributed routing. The experimental results show that DROCR algorithm achieves considerable performance gain over the equivalent tree routing at the highest depth examined. For supporting multi-dimensional range query, the experimental results indicate that the exponentially expanding and extending rate have been effectively controlled and minimized by HD Tree overlay structure and DROCR routing.     

In-network approximate computation of outliers with quality guarantees

Wireless sensor networks are becoming increasingly popular for a variety of applications. Users are frequently faced with the surprising discovery that readings produced by the sensing elements of their motes are often contaminated with outliers. Outlier readings can severely affect applications that rely on timely and reliable sensory data in order to provide the desired functionality. As a consequence, there is a recent trend to explore how techniques that identify outlier values based on their similarity to other readings in the network can be applied to sensory data cleaning. Unfortunately, most of these approaches incur an overwhelming communication overhead, which limits their practicality. In this paper we introduce an in-network outlier detection framework, based on locality sensitive hashing, extended with a novel boosting process as well as efficient load balancing and comparison pruning mechanisms. Our method trades off bandwidth for accuracy in a straightforward manner and supports many intuitive similarity metrics. Our experiments demonstrate that our framework can reliably identify outlier readings using a fraction of the bandwidth and energy that would otherwise be required.     

MIDS: a framework for information organization and discovery

The MITRE Information Discovery System (MIDS) is a baseline system for integrating advanced processing tools for information discovery and retrieval in large-scale distributed environments. The system is built on a modular, extendible architecture that allows for system-level decoupling and allocation of component processing tools across network nodes to provide for efficient processing in distributed environments. At one level, the system provides for multi-platform user access to HTTP, Gopher, FTP, and news servers using an HTML based client interface. However, more significantly, the system provides advanced tools for metadata generation from disparate network objects, and a content routing mediation layer for classification of metadata into appropriate information brokers. This bottom-up layered information organization approach supports a wide range of information retrieval and browsing strategies.     

基于向量空间的Web服务发现模糊方法

Web服务已逐渐发展成为重要的分布式计算范式。在综合分析了现有的Web服务描述文档的基础上,提出了一种基于模糊集的服务特征项集选取算法以及Web服务向量空间的生成方法。利用生成的向量空间,对Web服务进行模糊聚类。基于此,文中给出了向量空间中进行Web服务发现的模糊方法。所提出的方法只需利用现有的Web服务描述信息,保证了服务发现的有效性。     

The DR-tree: A Main Memory Data Structure for Complex Multi-dimensional Objects

An efficient index structure for complex multi-dimensional objects is one of the most challenging requirements in non-traditional applications such as geographic information systems, computer-aided design, and multimedia databases. In this paper we first propose a main memory data structure for complex multi-dimensional objects. Then, we present an extension of the existing multi-dimensional index structure. Among existing multi-dimensional index structures, the popular R*-tree is selected. The R*-tree is coupled with the main memory data structure to improve the performance of spatial query processing. An analytical model is developed for our index structure. Experimental results show that the analytical model is accurate, the relative error being below 15%. The performance of our index structure is compared with that of a state-of-the-art index structure by experimental measurements. Our index structure outperforms the state-of-the-art index structure due to its ability to reduce a large amount of storage.     

一种新的MDP算法的研究

提出了一种高效的挖掘数据仓库中多维关联规则的MDP算法。MDP算法通过构造一种扩展的前缀树MDP-tree,将数据仓库中的有效信息压缩存储,再使用基于MDP-tree的MDP-mining方法快速发现有趣的关联规则。MDP算法仅需要扫描一次数据仓库,就可以构造出MDP-tree,进而得到所有的关联规则。该算法还具有频繁模式查找简捷、二次查找迅速等优点。通过实验验证了MDP算法的高效性和稳定性,与传统的多维关联规则算法相比有更好的性能。     

基于用户行为特征的多维度文本聚类

传统多维度文本聚类一般是从文本内容中提取特征，而很少考虑数据中用户与文本的交互信息（如：点赞、转发、评论、关注、引用等行为信息），且传统的多维度文本聚类主要是将多个空间维度线性结合，没能深入考虑每个维度中属性间的关系。为有效利用与文本相关的用户行为信息，提出一种结合用户行为信息的多维度文本聚类模型（MTCUBC）。根据文本间的相似性在不同空间上应该保持一致的原则，该模型将用户行为信息作为文本内容聚类的约束来调节相似度，然后结合度量学习方法来改善文本间的距离，从而提高聚类效果。通过实验表明，与线性结合的多维度聚类相比，MTCUBC模型在高维稀疏数据中表现出明显的优势。     

定性空间推理中区域连接演算的多维扩展

区域连接演算(RCC)是定性空问推(QSR)的基础理论之一．但RCC理论只支持区域，不能处理包括点、线和区域在内的空问多维对象，这阻碍了RCC应用的发展．扩展了区域概念，将点和线对象视为特殊的区域．提出了能直接用RCC理论描述空间多维对象拓扑关系的MRCC理论．在保留RCC公理的前提下，MRCC增加了2条新公理，并由此推导出了36种MRCC基本关系．进而讨论了基于概念邻域图和复合表的推理．MRCC拓展了RCC理论的适用范围，促进了RCC向实际应用的发展．     

CISS: An efficient object clustering framework for DHT-based peer-to-peer applications

In most DHT-based peer-to-peer systems, objects are totally declustered since such systems use a hash function to distribute objects evenly. However, such an object de-clustering can result in significant inefficiencies in advanced access operations such as multi-dimensional range queries, continuous updates, etc, which are common in many emerging peer-to-peer applications. In this paper, we propose CISS (Cooperative Information Sharing System), a framework that supports efficient object clustering for DHT-based peer-to-peer applications. CISS uses a Locality Preserving Function (LPF) instead of a hash function, thereby achieving a high level of clustering without requiring any changes to existing DHT implementations. To maximize the benefit of object clustering, CISS provides efficient routing protocols for multi-dimensional range queries and continuous updates. Furthermore, our cluster-preserving load balancing schemes distribute loads without hotspots while preserving the object clustering property. We demonstrate the performance benefits of CISS through extensive simulation.     

基于本体的电力信息系统的语义集成研究

在语义网以及OWL等本体技术的基础上，构建了一种新型的信息集成系统（EOSIS）来实现电力企业信息的集成、语义连接及推理。其中包括EOSIS的业务需求分析、集成策略以及系统结构。EOSIS不同与现有的集成系统之处在于，它可以支持支持概念和对象的多维查询及导航、隐含业务信息推理、领域概念、事实的动态增加等功能。