View specification and manipulation for a semantic data model

Semantic data models are increasing in popularity and use, but they are also becoming increasingly complex and difficult to manage. In this paper we extend the definition of a semantic data model to give users the power to specify and manipulate views. Our model supports both high-level object-class views and high-level relationship-set views. To define these views, we extend the traditional method of view definition (through query formulation) to also include view definition by a dominant object class, by an independent object class, and by a relational object class. A set of operators to specify and manipulate views is also defined. These operators allow a user to create and destroy views, implode and explode views, hide and expose semantic-model elements. We also provide algorithms to extract an instance graph for a high-level object in a semantic-model view and to transform a semantic-model view hierarchy into an equivalent atomic model. Implications and applications of views in our model are also discussed.     

一个基于视图的数据访问模型

多用户共享一个数据库必然存在一些安全隐患,须加以特定的控制措施以防止非法访问。提出一个基于视图的数据访问模型(VBAC),根据用户名创建与之联系的视图(视图成为该用户访问属于他的数据的惟一窗口),回收所有用户的权限,并将视图的访问权限授予给与之对应的用户,当一个用户登录系统,将他与对应的视图绑定起来,用户的数据访问通过视图间接完成,一旦回收视图的授权,与之对应的用户将不能对数据库进行任何存取。通过授权的数据视图,将用户对数据的操纵限定在特定的行和列,在用户和数据库之间建立信息安全防火墙。在Microsoft SQL Server 2000下测试了该模型的有效性。     

关于面向对象数据库系统中用户视图机制的研究

面向对象数据库的模式是按照对象信息的内涵制定的,考虑的因素包括对象的分类、概括、综合、聚集及其所描述的不同类型对象间的联系等。然而不同用户对这些复杂信息的覆盖面有不同的要求,且不一定与系统的数据库模式恰好吻合,这就向面向对象数据库系统(OODBS)提出了支持用户视图、进行数据重构的要求。本文就引入用户视图机理到OODB 中的方法进行了探讨,给出了面向对象用户视图的定义与描述,并讨论了与之相关的数据字典信息,最后提出了建立用户视图所应遵循的原则。     

基于相似性学习的三维模型最优视图选择算法

针对已有最优视图度量难以适用于不同类型的三维模型,提出基于用户知识、在模型库中为各类模型建立最优视图样例,并在此基础上进行相似性学习,根据相似性度量获得输入模型最优视图的选择算法.首先采用AdaBoost算法对输入三维模型形状特征进行相似性学习,得到该模型的最优视图样例;然后将输入模型从不同视点得到的渲染视图和最优视图样例进行形状相似性分析,以相似度最高者作为输入模型的最优视图.实验结果表明,采用文中算法得到的最优视图不仅可以有效地逼近用户选择结果,而且具有较好的稳定性.     

IRP用户视图间依赖关系的度量

用户视图间的依赖关系对于信息资源规划中的数据分析和数据建模有着重要的意义。该文对用户视图间的依赖关系进行了定义和说明,并细分其为数据依赖和操作依赖,在此基础上,对用户视图间的依赖关系进行了度量,提出了依赖度和被依赖度2种度量方法,为规范用户视图提供了依据。     

Mobile multi-view object image search

High user interaction capability of mobile devices can help improve the accuracy of mobile visual search systems. At query time, it is possible to capture multiple views of an object from different viewing angles and at different scales with the mobile device camera to obtain richer information about the object compared to a single view and hence return more accurate results. Motivated by this, we propose a new multi-view visual query model on multi-view object image databases for mobile visual search. Multi-view images of objects acquired by the mobile clients are processed and local features are sent to a server, which combines the query image representations with early/late fusion methods and returns the query results. We performed a comprehensive analysis of early and late fusion approaches using various similarity functions, on an existing single view and a new multi-view object image database. The experimental results show that multi-view search provides significantly better retrieval accuracy compared to traditional single view search.     

A transparent schema-evolution system based on object-oriented viewtechnology

When a database is shared by many users, updates to the database schema are almost always prohibited because there is a risk of making existing application programs obsolete when they run against the modified schema. The paper addresses the problem by integrating schema evolution with view facilities. When new requirements necessitate schema updates for a particular user, then the user specifies schema changes to his personal view, rather than to the shared base schema. Our view schema evolution approach then computes a new view schema that reflects the semantics of the desired schema change, and replaces the old view with the new one. We show that our system provides the means for schema change without affecting other views (and thus without affecting existing application programs). The persistent data is shared by different views of the schema, i.e., both old as well as newly developed applications can continue to interoperate. The paper describes a solution approach of realizing the evolution mechanism as a working system, which as its key feature requires the underlying object oriented view system to support capacity augmenting views. We present algorithms that implement the complete set of typical schema evolution operations as view definitions. Lastly, we describe the transparent schema evolution system (TSE) that we have built on top of GemStone, including our solution for supporting capacity augmenting view mechanisms     

SERFing the web: The Re-Web approach for web re-structuring

In our emerging digital paper-less society, massive amount of information is being maintained in on-line repositories and diverse web site representations of this information must be served over the Internet to different user groups. E-commerce and digital libraries are two representative sample applications with such needs. In this paper we present a database-centric approach called Re-Web that addresses this need for flexible web site generation, re-structuring, and maintenance. Re-Web is based on two key ideas. First, we exploit the web site structure by associating web semantics (XML equivalents) with the modeling constructs of the ODMG object model to aid the web site generation process. By capturing the logical structure of web views within the OODB system, we can efficiently maintain the web views using standard database techniques. Secondly, to ease the process of specification and construction of multiple customized web view sites, we also propose the notion of generic web view transformations that are encapsulated into re-usable templates. Thus desired new web view sites can be generated simply by applying the corresponding transformations on the underlying database to produce web view classes and then by applying the web semantics on the newly built view classes. The Re-Web system has been implemented using PSE by Object Design Inc. as object repository, ODMG as object model, OQL as transformation language, SERF as OODB evolution facility and IBM XML parser and LotusXSL processor to aid the web site generation. A case study using Re-Web is also presented to illustrate the working of the system. To the best of our knowledge, Re-Web is the first web site management system focusing on the issue of re-usable view generation templates at the content and not at the presentation style level of abstraction. This revised version was published online in August 2006 with corrections to the Cover Date.     

View operations on objects with roles for a statically typeddatabase language

To deal with the evolution of data and applications and with the existence of multiple views for the same data, the object data model needs to be extended with two different sets of operations: object extension operations, to allow an object to dynamically change its type; and object viewing operations, to allow an object to be seen as if it had a different structure. Object extension and object viewing operations are related in that they are both identity-preserving operations, but different in that object extension may modify the behavior of the original object while object viewing creates a new view for the original object without modifying its behavior. A set of object viewing operations is defined in the context of a statically and strongly typed database programming language which supports objects with roles, and the relationships with object extension and role mechanisms are discussed. We then show how the object viewing operations can be used to give the semantics of a higher level mechanism to define views for object databases. Examples of the use of these operations are given with reference to the prototype implementation of the language Galileo 97     

Graphically Defining New Building Blocks in ThingLab

ThingLab is a constraint-oriented, interactive graphical system for building simulations. A typical problem in ThingLab (and in systems like it) is that, to define an object with a new kind of constraint, the user must leave the graphical domain and write code in the underlying implementation language. This makes it difficult for less experienced users to add new kinds of constraints or to modify existing ones. As a step toward solving this problem, the system described here allows the graphical definition of objects that include new kinds of constraints. This is supported by an interface in which a user can open two views on an object being defined, a use view and a construction view. The use view shows the object's normal appearance; the construction view contains additional objects and constraints, which serve to graphically specify the new constraints on the defined object.     

三维重建中的剖视图处理

剖视图处理能够有助于更好地理解视图,提高三维重建的效率。基于对剖视图自身特点的分析,提出了三维重建中对剖视图的处理算法,即通过剖视图信息的智能提取生成基元体,将基元体同由视图轮廓生成的参照体进行布尔运算,从而得到最终的目标体。算法能够处理包括全剖视图、半剖视图以及平行剖视图在内的剖视图,最后给出了应用算例以验证算法的可行性。     

A scenario-based object-oriented hypermedia design methodology

This paper defines an object-oriented methodology for developing hypermedia information systems. The methodology consists of six phases: domain analysis; object modeling; view design; navigation design; implementation design; and construction. Users' requirements are analyzed with a responsibility-driven technology using scenarios. Object-oriented views are generated as the result of object modeling, and then used for the subsequent navigation and implementation design. The implementation design phase deals with database schema, page structure and flow, and user interface. This methodology integrates enterprise databases with distributed hypermedia systems via Internet, Intranet, or Electronic Commerce.     

Importance-driven focus of attention

This paper introduces a concept for automatic focusing on features within a volumetric data set. The user selects a focus, i.e., object of interest, from a set of pre-defined features. Our system automatically determines the most expressive view on this feature. A characteristic viewpoint is estimated by a novel information-theoretic framework which is based on the mutual information measure. Viewpoints change smoothly by switching the focus from one feature to another one. This mechanism is controlled by changes in the importance distribution among features in the volume. The highest importance is assigned to the feature in focus. Apart from viewpoint selection, the focusing mechanism also steers visual emphasis by assigning a visually more prominent representation. To allow a clear view on features that are normally occluded by other parts of the volume, the focusing for example incorporates cut-away views.     

Navigation Tools for Viewing Augmented CAD Models

The first step in the development of any modern physical product is the construction of a CAD model. This model will be used during the product's complete life cycle: prototyping, fabrication, maintenance, and upgrading. During construction, a discrepancy can occur between the model and the object. To maintain and upgrade the object, the model must represent the reality. Keeping the model up to date requires verifying and sometimes updating it. A proposed scalable solution augments CAD software with pictures of the object. This approach aligns still images to the model, allowing visualization of the model and the object at the same time. This creates a mixed view. The virtual camera that renders the model in a mixed view is restricted by the still image because the alignment between the image and the model must be maintained. A tool helps users navigate in this view by transposing the zoom and pan from 2D user interfaces. Other tools allow intuitive navigation within a set of mixed views. This article is part of a special issue on 3D user interfaces.     

一种实化视图的合并算法

对于拥有大量实化视图的实际数据库应用系统,提出了视图合并的方法以减少整个视图 的数量,缩减实化视图的搜索空间;还提出了归并树和基于归并树的快速有效的合并算法。实验表 明,实化视图的合并是快速寻找可能响应查询的实化视图的一种有效途径,可以显著改进查询处理的 性能。     

融合信息熵和CNN 的基于手绘的三维模型检索

基于手绘草图的三维模型检索(SBSR)已成为三维模型检索、模式识别与计算机视 觉领域的一个研究热点。与传统方法相比,基于卷积神经网络(CNN)的三维深度表示方法在三 维模型检索任务中性能优势非常明显。本文提出了一种基于手绘图像融合信息熵和CNN 的三 维模型检索方法。首先,通过计算模型投影图的信息熵得到模型的代表性视图,并将代表性视 图经过边缘检测等处理得到三维模型投影图的轮廓图像;然后,将轮廓图像和手绘草图输入到 CNN 中提取特征描述子,并进行特征匹配。本文方法在Shape Retrieval Contest (SHREC) 2012 数据库和SHREC 2013 数据库上进行实验。实验证明,该方法的效果较其他传统方法检索准确 度更高。     

基于Web视图模型构建生物信息二级数据库

提出采用带根连通有向图来描述生物信息二级数据库的Web视图模型，以结合生物信息背景知识设计特定的生物信息Web视图及其问的相关关系．通过常量、静态和动态三类视图构成的Web视图模型解决了生物信息计算与数据资源共享的统一概念抽象．据此构建的硒蛋白相关生物信息二级数据库不仅可提供常规的数据管理和发布服务，并且将各类基因序列、蛋白质序列等生物信息数据的发布、蛋白质结构观察等Web计算有机地联系起来，符合分子生物学中信息流的观点．     

Type-level access pattern view: Enhancing prefetching performance using the iterative and recursive patterns

Since recent applications such as XML applications, Geographical Information Systems (GIS), and CAD/CAM systems require highly efficient data management, they are built on Object-Relational DBMS (ORDBMS). The applications are called navigational applications, and they navigate the composite objects connected via the reference and the collection attributes in the ORDBMS. When a navigational application accesses an object, it first checks whether the object is stored in the object cache. If not, the object must be fetched from the database in the server, which is a costly operation. Prefetching identifies the objects that are most likely to be accessed in the near future by the navigational applications and stores them in the object cache in advance. Since prefetching reduces the number of object fetches, it is crucial for improving the application performance. However, the experimental result by Han et al. [16] showed that the improvement ratio of application performance is much lower than the reduction ratio of the number of object fetches.In this paper, we claim that the number of disk accesses in the server also considerably affects the application performance, and we propose a technique for minimizing disk accesses to improve the performance of the prefetch method by Han et al. [16] and hence the navigational application. The contributions of this paper are summarized as follows. (1) For the iterative and the recursive patterns, we propose methods for creating materialized views based on the type-level path access logs proposed in [15]. We refer to the materialized views as the type-level access pattern views. (2) We then present the algorithms for minimizing the number of disk accesses using the type-level access pattern views when prefetching the objects from the database in the server. (3) We present an implementation technique that, given a prefetch request from the client, quickly finds the most efficient type-level access pattern view. (4) We perform a series of experiments using a variety of databases to show that the proposed technique significantly improves the overall performance of the navigational application. Experimental result shows that we reduce the number of disk accesses by up to 33.0 times and improve the performance by up to 21.4 times.     

Using object deputy model to prepare data for data warehousing

Providing integrated access to multiple, distributed, heterogeneous databases and other information sources has become one of the leading issues in database research and the industry. One of the most effective approaches is to extract and integrate information of interest from each source in advance and store them in a centralized repository (known as a data warehouse). When a query is posed, it is evaluated directly at the warehouse without accessing the original information sources. One of the techniques that this approach uses to improve the efficiency of query processing is materialized view(s). Essentially, materialized views are used for data warehouses, and various methods for relational databases have been developed. In this paper, we first discuss an object deputy approach to realize materialized object views for data warehouses which can also incorporate object-oriented databases. A framework has been developed using Smalltalk to prepare data for data warehousing, in which an object deputy model and database connecting tools have been implemented. The object deputy model can provide an easy-to-use way to resolve inconsistency and conflicts while preparing data for data warehousing, as evidenced by our empirical study.