A survey of database design transformations based on the Entity-Relationship model

At present, the Entity-Relationship (ER) model is the most important paradigm for conceptual database design. Since the model was introduced in the mid-seventies, a large body of literature has been published on transforming conceptual ER schemas or diagrams into logical data models. The purpose of this paper is to survey this literature. A first focus is on transformation approaches from the ER model to traditional data models, i.e. to the relational, the network, or the hierarchical model; this is then complemented by a discussion of more recent transformations to object-oriented models. A second focus is on considering the process of reverse engineering, i.e. transformations from a logical model back into the ER model; finally, an overview of direct transformations between various logical data models is presented.     

Automatic integration of Web search interfaces with WISE-Integrator

An increasing number of databases are becoming Web accessible through form-based search interfaces, and many of these sources are database-driven e-commerce sites. It is a daunting task for users to access numerous Web sites individually to get the desired information. Hence, providing a unified access to multiple e-commerce search engines selling similar products is of great importance in allowing users to search and compare products from multiple sites with ease. One key task for providing such a capability is to integrate the Web search interfaces of these e-commerce search engines so that user queries can be submitted against the integrated interface. Currently, integrating such search interfaces is carried out either manually or semiautomatically, which is inefficient and difficult to maintain. In this paper, we present WISE-Integrator - a tool that performs automatic integration of Web Interfaces of Search Engines. WISE-Integrator explores a rich set of special metainformation that exists in Web search interfaces and uses the information to identify matching attributes from different search interfaces for integration. It also resolves domain differences of matching attributes. In this paper, we also discuss how to automatically extract information from search interfaces that is needed by WISE-Integrator to perform automatic interface integration. Our experimental results, based on 143 real-world search interfaces in four different domains, indicate that WISE-Integrator can achieve high attribute matching accuracy and can produce high-quality integrated search interfaces without human interactions.Received: 2 January 2004, Accepted: 25 March 2004, Published online: 12 August 2004Edited by: M. Carey     

XML在故障树分析软件中的应用

XML是树结构的文本文件，可以完整的保存故障树信息.本文时XML在故障树分析软件中的应用进行了研究，并试着给出了一个的XML构架和如何把故障树转化为XML文件。     

0．18μm 12GHz CMOS八分频电路设计

提出了一种基于高速锁存器的CMOS高速分频器结构，阐述了其工作速度，工作范围，前后级级联电路设计。采用典型的TSMC0．18μm／1．8V工艺模型，通过Agilent的ADS进行模拟验证，得到其最高工作速度为12GHz，工作范围为3～12GHz，在6～12GHz内，输入灵敏度不小于100mV，功耗小于28mw。     

低抖动的鉴频鉴相器设计

提出一种SCL结构差分型鉴频鉴相器(PFD),这种鉴频鉴相器能大幅度降低鉴相死区,而且具有噪声低、速度快等优点.这种差分型PFD在高速、低抖动、低噪声PLL中有着广泛的应用.该电路基于chartered 0.35μm CMOS工艺,并用MENTOR eldo进行仿真,仿真结构表明,该PFD死区只有0.03ns.并且可以大大降低VCO控制电压的波纹.     

基于Schema标准的XML函数依赖及推理规则

针对DTD标准的一些局限性,国际互联网联盟推出了Schema标准.通过分析DTD标准和Schema标准的不同之处,并参考基于DTD标准的XML函数依赖的相关研究,提出了Schema的形式化定义等一系列基础概念,给出了基于Schema标准的XML函数依赖定义以及它的推理规则集,有助于规范化XML文档和今后的研究工作.     

Wrapping of Web Sources with restricted Query Interfaces by Query Tunneling

Information sources in the World Wide Web usually offer two different schemes to their users, an Interface Schema which the user can query and a Result Schema which the user can browse. Often the Interface Schema is more restricted than the Result Schema, moreover many sources offer keyword-search interfaces only. Thus query capabilities of such sources are very small and a useful integration into a mediator-based information system using query capabilities is almost impossible. We propose the Query Tunnelling architecture for the wrapping of these restricted web sources. Wrapping of sources by Query Tunneling hides restrictive query interfaces and makes such sources fully queryable based on their result schema. The process of Query Tunneling is divided into two main steps, Query Relaxation to make a higher order query suitable to a restricted interface and Result Restriction in order to filter the results using the original query.     

XML Schema视图的研究与实现

XML技术的应用范围越来越广泛,XML文档中可能包含敏感程度不同的信息,需要进行访问控制。视图是一种常用、有效的细粒度访问控制手段。而基于角色访问控制是一种灵活、高效的访问控制策略。以基于角色访问控制为例,给出了基于Schema的授权策略文档设计,并讨论了XML Schema视图的生成算法和基于XML Schema视图实现访问控制的体系结构。     

基于LDAP的PKI证书的存储与备份

本文较深入地介绍了LDAP协议在PKI体系中的应用,主要讲遂了如何利用LDAP服务器存储以及备份电子证书。首先简单阐明了目录服务的优点,然后根据存储的需要自定义了LDAP中的属性,并扩展了一个对象类,最后描述了LDAP服务的复制和均衡负载模型。     

数据库应用系统逻辑结构设计初探

数据库应用系统的逻辑设计是建立数据库应用系统过程中最为重要的一环。主要就如何科学合理地进行数据库系统逻辑设计,从E—R图向数据模型的转换、关系模式的规范化、改善优化数据库性能、存储空间的调整等四个方面进行分析和讨论。