演员模型：一种多媒体数据表达模型

本文提出一种多媒体数据表达模型：演员模型，该模型建立在多媒体数据库概念模型基础之上，基于库所—时间Ｐｅｔｒｉ网，描述多媒体对象之间的时态关系，同时引入与变迁相关联的场景表达式，描述多媒体对象之间的空间关系，从而模拟多媒体数据的时空编组，文中形式化地定义了演员模型的抽象模型和实现模型，提出多媒体对象的表达算法以及多媒体数据库的查询模型．     

异构数据源数据集成的研究

对象代理模型可以作为数据集成的一种通用数据模型。通过建立代理对象和源对象,查询处理的对应关系也能够较好地实现,应用可以将不同的、对于代理对象的查询处理翻译成对于局部数据源源对象的查询处理,也可以把对局部数据源的查询结果以用户应用想要的方式返回。对象代理模型可在Smalltalk环境中实现。本文讨论如何在Smalltalk
k环境中实现基于对象代理模型的异构信息源的集成。     

移动对象数据库模型、查询语言及实时交通流分析

提出一种移动对象数据库模型——Dynamic Transportation Network Based Moving Objects Database(简称DTNMOD),并给出了DTNMOD中基于移动对象时空轨迹的网络实时动态交通流分析方法.在DTNMOD中,交通网络被表示成动态的时空网络,可以描述交通状态、拓扑结构以及交通参数随时间的变化过程;网络受限的移动对象则用网络移动点表示.DTNMOD 模型包含了完整的数据类型和查询操作的定义,因此可以在任何可扩充数据库(如PostgreSQL 或SECONDO)中实现,从而得到完整的数据库模型和查询语言.为了对相关模型的性能进行比较与分析,基于PostgreSQL 实现了一个原型系统并进行了一系列的实验.实验结果表明,DTNMOD 提供了良好的区域查询及连接查询性能.     

Foundations for object-oriented query processing

A minimal framework for an object-oriented query language standard should (1) include a formal definition of a high-level data model and the syntax and semantics of associated query languages, (2) provide the functionality of relational query languages, and (3) support proofs of correctness of transformations for logical query optimization. In this paper, a high-level conceptual model for object-oriented query processing is discussed; the model includes widely-used structural abstractions such as the isa relationship, associations (properties) between complex objects and complex objects/values, and inheritance of properties. A formal, algebraic query language for the model, inspired by relational algebra, is presented. Operators of the algebra allow queries based on values, queries that manipulate entire objects, and queries that construct new objects from existing objects/values. All queries retain connections to existing database objects, providing logical access paths to data. Each query result is a class, so the algebra has the closure property. The intensional and extensional results of query operators are summarized. Two forms of logical query optimization supported by the query algebra are outlined: algebraic transformations and classifier-based optimizations (optimizations which employ inclusion and exclusion dependencies between classes).     

Modeling and querying fuzzy spatiotemporal databases

Modeling spatiotemporal data, in particular fuzzy and complex spatial objects representing geographic entities and relations, is a topic of great importance in geographic information systems, computer vision, environmental data management systems, etc. Because of complex requirements, it is challenging to represent spatiotemporal data and its features in databases and to effectively query them. This article presents a new approach to model and query the spatiotemporal data of fuzzy spatial and complex objects and/or spatial relations. In our case study, we use a meteorological database application in an intelligent database architecture, which combines an object-oriented database with a knowledgebase for modeling and querying spatiotemporal objects.     

移动对象的动态反向k最近邻研究

反向最近邻查询是空间数据库中最重要的算法之一。传统的反向最近邻查询方法主要是针对静态对象的查询,随着无线通讯和定位技术的快速发展,移动对象发出的查询请求成为新的研究热点。该文将TPR-tree作为算法的索引结构,并提出了基于矩形框的对角线的修剪策略,将半平面修剪策略进行改进,给出了移动对象的动态反向k最近邻的查询方案。     

Pictorial Query Specification for Browsing Through Spatially Referenced Image Databases

A pictorial query specification technique that enables the formulation of complex pictorial queries for browsing through a collection of spatially referenced images is presented. It is distinguished from most other methods by the fact that in these methods the query image specifies a target database image in its entirety whereas in our approach the query image specifies the combination of objects that the target database image should contain rather than being treated as a whole image. The query objects are represented by shape features although other features such as color, texture or wavelets could also be used. Using our technique, it is possible to specify which particular objects should appear in the target images as well as how many occurrences of each object are required. Moreover, it is possible to specify the minimum required certainty of matching between query-image objects and database-image objects, as well as to impose spatial constraints that specify bounds on the distance between objects and the relative direction between them. These spatial constraints can also be used to specify other topological relations such as enclosure, intersection, overlap, etc. Each pictorial query is composed of one or more query images. Each query image is constructed by selecting the required query objects and positioning them according to the desired spatial configuration. Boolean combinations of two or more query images are also possible by use of AND and OR operators. A query image may be negated in order to specify conditions that should not be satisfied by the database images that are retrieved successfully. In addition, a capability is provided to specify whether the same instance of an object is to be used when it appears in more than one of the query images that make up the pictorial query, or whether two different instances are allowed. Several example queries are given that demonstrate the expressive power of this query specification method. An algorithm for retrieving all database images that conform to a given pictorial query specification is presented. The user interface for using this pictorial query specification method to browse the results in a map image database application is described and illustrated via screen shots.     

The living in a lattice rule language

This paper presents a rule-based query language for an object-oriented database model. The database model supports complex objects, object identity, classes and types, and a class/type hierarchy. The instances are described by ‘object relations’ which are functions from a set of objects to value sets and other object sets. The rule language is based on object-terms which provide access to objects via the class hierarchy. Rules are divided into two classes: object-preserving rules manipulating existing objects (yielding a new ‘view’ on objects available in the object base) and object-generating rules creating new objects with properties derived from existing objects. The derived object sets are included in a class lattice. We give conditions for whether the instances of the ‘rules’ heads are ‘consistent’, i.e. represent object relations where the properties of the derived objects are functionally determined by the objects.     

分布式数据库系统中的查询优化处理

分布式查询处理是用户与分布式数据库的接口,也是分布式数据库研究的主要问题之一。在分布式查询处理中基于不同的目标有不同的查询优化算法,文章主要讨论基于最小传输代价原则的半连接算法,分析了半连接算法的原理并给出了多关系半连接查询优化算法思考。     

Shapeme histogram projection and matching for partial object recognition

Histograms of shape signature or prototypical shapes, called shapemes, have been used effectively in previous work for 2D/3D shape matching and recognition. We extend the idea of shapeme histogram to recognize partially observed query objects from a database of complete model objects. We propose representing each model object as a collection of shapeme histograms and match the query histogram to this representation in two steps: 1) compute a constrained projection of the query histogram onto the subspace spanned by all the shapeme histograms of the model and 2) compute a match measure between the query histogram and the projection. The first step is formulated as a constrained optimization problem that is solved by a sampling algorithm. The second step is formulated under a Bayesian framework, where an implicit feature selection process is conducted to improve the discrimination capability of shapeme histograms. Results of matching partially viewed range objects with a 243 model database demonstrate better performance than the original shapeme histogram matching algorithm and other approaches.     

Functional Query Optimization over Object-Oriented Views for Data Integration

AMOS is a mediator system that supports passive (non-intrusive) integration of data from heterogeneous and autonomous data sources. It is based on a functional data model and a declarative functional query language AMOSQL. Foreign data sources, e.g., relational databases, text files, or other types of data sources can be wrapped with AMOS mediators, making them accessible through AMOSQL. AMOS mediators can communicate among each other through the multi-database constructs of AMOSQL that allow definition of functional queries and OO views accessing other AMOS servers. The integrated views can contain both functions and types derived from the data sources. Furthermore, local data associated with these view definitions may be stored in the mediator database. This paper describes AMOS' multi-database query facilities and their optimization techniques. Calculus-based function transformations are used to generate minimal query expressions before the query decomposition and cost-based algebraic optimization steps take place. Object identifier (OID) generation is used for correctly representing derived objects in the mediators. A selective OID generation mechanism avoids overhead by generating in the mediator OIDs only for those derived objects that are either needed during the processing of a query or have associated local data in the mediator database. The validity of the derived objects that are assigned OIDs and the completeness of queries to the views are guaranteed by system generated predicates added to the queries.     

多媒体数据库的时态索引技术

针对多媒体数据库中具有时态特性的媒体对象，提出一种基于区间的索引机制，目的是为了提高时间检索的性能。这种时态索引可以快速查找任意时间段中的时态对象，它能有效地支持多种时态关系操作符；支持多种时态集函数；支持时态ＪＯＩＮ操作等等。该索引支持媒体展示过程。     

Efficient processing of probabilistic reverse nearest neighbor queries over uncertain data

Reverse nearest neighbor (RNN) search is very crucial in many real applications. In particular, given a database and a query object, an RNN query retrieves all the data objects in the database that have the query object as their nearest neighbors. Often, due to limitation of measurement devices, environmental disturbance, or characteristics of applications (for example, monitoring moving objects), data obtained from the real world are uncertain (imprecise). Therefore, previous approaches proposed for answering an RNN query over exact (precise) database cannot be directly applied to the uncertain scenario. In this paper, we re-define the RNN query in the context of uncertain databases, namely probabilistic reverse nearest neighbor (PRNN) query, which obtains data objects with probabilities of being RNNs greater than or equal to a user-specified threshold. Since the retrieval of a PRNN query requires accessing all the objects in the database, which is quite costly, we also propose an effective pruning method, called geometric pruning (GP), that significantly reduces the PRNN search space yet without introducing any false dismissals. Furthermore, we present an efficient PRNN query procedure that seamlessly integrates our pruning method. Extensive experiments have demonstrated the efficiency and effectiveness of our proposed GP-based PRNN query processing approach, under various experimental settings.     

Similar-shape retrieval in shape data management

Addresses the problem of similar-shape retrieval, where shapes or images in a shape database that satisfy specified shape-similarity constraints with respect to the query shape or image must be retrieved from the database. In its simplest form, the similar-shape retrieval problem can be stated as, “retrieve or select all shapes or images that are visually similar to the query shape or the query image's shape”. We focus on databases of 2D shapes-or equivalently, databases of images of flat or almost flat objects. (We use the terms “object” and “shape” interchangeably). Two common types of 2D objects are rigid objects, which have a single rigid component called a link, and articulated objects, which have two or more rigid components joined by movable (rotating or sliding) joints. An ideal similar-shape retrieval technique must be general enough to handle images of articulated as well as rigid objects. It must be flexible enough to handle simple query images, which have isolated shapes, and complex query images, which have partially visible, overlapping or touching objects. We discuss the central issues in similar-shape retrieval and explain how these issues are resolved in a shape retrieval scheme called FIBSSR (Feature Index-Based Similar-Shape Retrieval). This new similar-shape retrieval system effectively models real-world applications     

移动对象查询研究进展

移动对象查询技术是目前数据库技术研究的热点。移动对象的查询处理技术不仅要追求高效率和高精确度,而且要充分考虑到现实可行性和不同维度空间的可拓展性。本文基于前人对移动对象查询的分类方法,根据移动对象查询的发展动态,将移动对象查询分为轨迹查询和坐标查询两大类;回顾了已有的各种查询处理方法,分析了各种方法的优缺点,并且基于方法间的继承性和互补性,为后续的查询研究提出了建议。     

Window Query Processing in Linear Quadtrees

The linear quadtree is a spatial access method that is built by decomposing the spatial objects in a database into quadtree blocks and storing these quadtree blocks in a B-tree. The linear quadtree is very useful for geographic information systems because it provides good query performance while using existing B-tree implementations. An algorithm and a cost model are presented for processing window queries in linear quadtrees. The algorithm can handle query windows of any shape in the general case of spatial databases with overlapping objects. The algorithm recursively decomposes the space into quadtree blocks, and uses the quadtree blocks overlapping the query window to search the B-tree. The cost model estimates the I/O cost of processing window queries using the algorithm. The cost model is also based on a recursive decomposition of the space, and it uses very simple parameters that can easily be maintained in the database catalog. Experiments with real and synthetic data sets verify the accuracy of the cost model.     

Evolutionary Algorithms for Allocating Data in Distributed Database Systems

A major cost in executing queries in a distributed database system is the data transfer cost incurred in transferring relations (fragments) accessed by a query from different sites to the site where the query is initiated. The objective of a data allocation algorithm is to determine an assignment of fragments at different sites so as to minimize the total data transfer cost incurred in executing a set of queries. This is equivalent to minimizing the average query execution time, which is of primary importance in a wide class of distributed conventional as well as multimedia database systems. The data allocation problem, however, is NP-complete, and thus requires fast heuristics to generate efficient solutions. Furthermore, the optimal allocation of database objects highly depends on the query execution strategy employed by a distributed database system, and the given query execution strategy usually assumes an allocation of the fragments. We develop a site-independent fragment dependency graph representation to model the dependencies among the fragments accessed by a query, and use it to formulate and tackle data allocation problems for distributed database systems based on query-site and move-small query execution strategies. We have designed and evaluated evolutionary algorithms for data allocation for distributed database systems.     

基于对象关系数据库的移动对象数据库管理系统的研究

基于对象关系数据库设计了一个移动对象的数据模型,查询语言和相应的数据库管理系统。此系统结合GIS数据库系统能够表述移动物体和支持对运动物体的查询,从而实现基于位置的服务。本系统支持不确定性和复杂可扩展的空间结构,最后描述了这个系统的执行与实现。