基于XML模式的作业描述语言的设计与处理

作业描述语言为远程教育中的Web作业管理系统，提供了一套基于XML的分割、表示与处理半结构化作业数据的解决方案，并可为异构型作业管理系统之间交换作业文档提供一种技术规范。介绍了基于XML模式的作业描述语言的设计过程与使用方法，并对XML作业文档的验证、显示与存储等处理方式进行了讨论。     

Converting relational database into XML documents with DOM

The revolution of XML is recognized as the trend of technology on the Internet to researchers as well as practitioners. Companies need to adopt XML technology. With investment in the current relational database systems, they want to develop new XML documents while running existing relational databases on production. They need to reengineer the relational databases into XML documents with constraints preservation. In the process, schema translation must be done before data conversion. Since the existing relational databases are usually normalized, they have to be reconstructed into XML document tree structures. This can be accomplished through denormalization by joining the normalized relations into tables according to their data dependencies constraints. The joined tables are mapped into DOMs, which are then integrated into XML document trees. The user specifies an XML document root with its relevant nodes to form a partitioned XML document tree to meet their requirements. The selected XML document tree is mapped into an XML schema in the form of DTD. We then load joined tables into DOMs, integrate them into a DOM, and transform it into an XML document.     

一种基于操作集计算生成有效XML文档的方法

目前XML工具的编辑能力不足以保证生成有效的XML文档,缺乏对文档模式的合理利用。而由XMLSchema定义的文档模式,不仅提供了有效性验证标准,同时蕴含了生成有效XML文档的准则。本文提出了一种生成有效XML文档的方法。该方法基于XML文档模式图定义不同节点的操作集合,以及该操作集合上的计算和相应操作语义,并分析论证了该方法本身的有效性。     

一种XML文档模式有效性验证算法

XML Schema作为XML文档模式的定义语言,其语法本身不能保证定义模式的有效性。该文首先分析影响XML文档模式有效性的因素,并构造了XML文档模式图。依据XML实例文档特点,分析了XML文档模式图性质,其中包括递归引用可能导致死锁发生的原因。最后,给出了XML文档模式有效性验证算法,从而弥补了常见验证工具功能的不完整。     

保持数据约束的关系数据库至XML文档的转换

XML已成为Internet上的技术趋势,在保留原有关系数据库的同时发展XML文档是目前的最佳选择,它需要在保持数据依赖约束基础上实现关系数据库与XML文档的转换.这一过程中,模式转换必须先于数据转换,因为现有的关系数据库通常是规范化的,重建XML文档树结构才能实现这一转换.为了达成此目的,首先依据已有的数据依赖约束将规范化的关系联合进一组表格,实现反向规范化,然后将这些联合表格映射为一组DOM,归并成XML文档树,根据用户选择的根结点,以及与它相连的结点形成一个期望的局部文档树,被选的XML文档树又映射为DTD格式的XML模式.这样就可以将联合表映射成一组DOM,并将其归并成单一DOM,最终转换成XML文档.     

The Query Language to XML Documents Connected by XLink Links

The XML linking language (XLink) is a language for describing links between resources by means of XML attributes and a special namespace. The specification of the XLink language developed by the World Wide Web consortium provides only data structures for describing links and a minimal model of their behavior. In this paper, a language that allows the application to transparently formulate queries to XLink links and traverse the arcs determined by these links is suggested. The suggested language was named XPathLink, since it was developed as a natural extension of XPath, the language for addressing structural parts of XML documents. The XPathLink encapsulates complexities of XLink syntax from the application and provides a higher abstraction level when processing a set of XML documents connected by XLink links compared to the existing approaches. An implementation of the suggested XPathLink language by functional methods is considered. The functionality of the query language to XML documents connected by XLink links is achieved owing to the integration of the suggested implementation with the general-purpose programming language Scheme at the level of nodes of the processed XML documents and Scheme functions.__________Translated from Programmirovanie, Vol. 31, No. 3, 2005.Original Russian Text Copyright © 2005 by Lizorkin.     

一种支持动态 XML 文档的存储模式设计与应用

针对XRel模式无法有效支持动态XML文档存储的问题,在区间编码的基础上,引入向量方法提出一种支持XML文档动态更新的编码方案——NewDietz,设计可以存储NewDietz编码元素的关系模式,并给出新元素在关系模式下的更新方法。新模式既保证新元素的有效存储,又兼顾动态XML文档从该模式中重组需要对元素进行祖先-后裔判断的问题。为验证新模式的实际应用效果,开发一个水利空间数据存储与展示模块,并对空间数据分别采用2种存储模式进行验证。对比结果表明,新模式明显提升XML文档在关系数据库中的存储效率,并有效支持XML文档的动态更新,为基于XML的水利业务数据在关系数据库中的高效存储提供一种可能。     

用UML设计XML文档模式

XML是新一代的置标语言,它定义了一种描述数据、交换数据的标准。W3CXMLSchema是定义和描述XML文档结构的模式语言。UML是一种得到广泛应用的标准对象建模语言。文章以B2C中的电子定单为例,描述了用UML设计XML文档模式的方法。     

一种基于XML Schema的安全访问控制策略

为提高XML文档资源访问控制的安全性,依据RBAC对XML组件具有复杂约束以及模式与元素之间关系的良好重用机制的特性,构建了一种新的访问控制模型—SRBAC。在此基础上,提出了相应目标访问控制算法TDACA,创建了相应策略,验证了SRBAC的有效性,从而实现了有效的访问控制和实例级的认证,保证了XML文件的安全使用。     

XML Schema与DTD的比较及应用

XML是目前广泛应用的数据交换标准，而模式是应用XML进行数据交换的正确性的保证机制之一。模式详细描述了文档的结构，确保文档的元素和属性等的正确性。XML Schema和DTD是其中应用最广泛的模式。文中详细比较了两者的异同，并指出了各自的局限及最佳的应用，DTD非常适合于文本密集型XML文档，而XML Schema更适合于数据密集型XML文档。     

XML数据的结构化处理方法

越来越多的数据采用XML格式表示和交换，对XML数据的有效访问方法是目前需要解决的关键问题之一．对通过面向对象数据库系统访问XML数据的方法进行了讨论，提出了将XML数据映射到对象模型的规则以及建立XML数据的OODB模式的方法．为了建立高效地访问路径提出了一种XML数据的结构索引，并介绍了利用结构索引实现基本的数据操作的方法．实验结果表明，提出的方法具有较高的效率。     

Authorization Translation for XML Document Transformation

XML access control models proposed in the literature enforce access restrictions directly on the structure and content of an XML document. Therefore access authorization rules (authorizations, for short), which specify access rights of users on information within an XML document, must be revised if they do not match with changed structure of the XML document. In this paper, we present two authorization translation problems. The first is a problem of translating instance-level authorizations for an XML document. The second is a problem of translating schema-level authorizations for a collection of XML documents conforming to a DTD. For the first problem, we propose an algorithm that translates instance-level authorizations of a source XML document into those for a transformed XML document by using instance-tree mapping from the transformed document instance to the source document instance. For the second problem, we propose an algorithm that translates value-independent schema-level authorizations of non-recursive source DTD into those for a non-recursive target DTD by using schema-tree mapping from the target DTD to the source DTD. The goal of authorization translation is to preserve authorization equivalence at instance node level of the source document. The XML access control models use path expressions of XPath to locate data in XML documents. We define property of the path expressions (called node-reducible path expressions) that we can transform schema-level authorizations of value-independent type by schema-tree mapping. To compute authorizations on instances of schema elements of the target DTD, we need to identify the schema elements whose instances are located by a node-reducible path expression of a value-independent schema-level authorization. We give an algorithm that carries out path fragment containment test to identify the schema elements whose instances are located by a node-reducible path expression.     

XML materialized views and schema evolution in VIREX

Web-based databases are gaining increased popularity. This has positively influenced the availability of structured and semi-structured databases for access by a variety of users ranging from professionals to naive users. The number of users accessing online databases will continue to increase if the visual tools connected to web-based databases are flexible and user-friendly enough to meet the expectations of naive users and professionals. Further, XML is accepted as the standard for platform independent data exchange. This motivated for the development of the conversion tools between structured databases and XML. Realizing that such a need has not been well handled by the available tools, including Clio from IBM, we developed VIREX as a visual tool for converting relational databases into XML, and since then has been empowered with further capabilities to manipulate the produced XML schema including the maintenance of materialized views and schema evolution functions. VIREX provides an interactive approach for querying and integrating relational databases to produce XML documents and the corresponding XML schema(s). VIREX supports VRXQuery as a visual naive users-oriented query language that allows users to specify queries and define views directly on the interactive diagram as a sequence of mouse clicks with minimum keyboard input. As the query result, VIREX displays on the screen the XML schema that satisfies the specified characteristics and generates colored (easy to read) XML document(s). The main contribution described in this paper is the novel approach for turning query results into materialized views which are maintained to remain consistent with the underlying database. VIREX supports deferred update of XML views by keeping an ordered summary of the necessary and sufficient information required for the process. Each view has a corresponding marker in the ordered summary to indicate the start of the information to be reflected onto the view when it is accessed. When a view is accessed, its marker moves to the head of the list to mark for the next update. In addition, VIREX supports some basic schema evolution functions include renaming, adding and dropping of elements and attributes, among others. The supported schema evolution functions add flexibility to the view maintenance and materialization process.     

Dual syntax for XML languages

XML is successful as a machine processable data interchange format, but it is often too verbose for human use. For this reason, many XML languages permit an alternative more legible non-XML syntax. XSLT stylesheets are often used to convert from the XML syntax to the alternative syntax; however, such transformations are not reversible since no general tool exists to automatically parse the alternative syntax back into XML.

We present XSugar, which makes it possible to manage dual syntax for XML languages. An XSugar specification is built around a context-free grammar that unifies the two syntaxes of a language. Given such a specification, the XSugar tool can translate from alternative syntax to XML and vice versa. Moreover, the tool statically checks that the transformations are reversible and that all XML documents generated from the alternative syntax are valid according to a given XML schema.     

基于分治策略的XML文档更新计算

XML文档更新是XML数据管理的重要功能,对XML文档进行插入更新操作时面临编码调整问题,目前大部分编码方案并不能很好支持文档更新。在分析现有编码方案基础上,提出了OMPN(order, maxOrder, parentOrder, nextOrder)编码方案,采用分治策略和迟后更新方法,在插入节点过程中不需要调整编码,在计算资源空闲时,只需调整部分编码就可以完成对XML文档的更新。实验结果表明,基于分治策略和迟后更新方法提高了更新XML文档的性能。     

Constraint Preserving Transformation from Relational Schema to XML Schema

XML has become the standard for publishing and exchanging data on the Web. However, most business data is managed and will remain to be managed by relational database management systems. As such, there is an increasing need to efficiently and accurately publish relational data as XML documents for Internet-based applications. One way to publish relational data is to provide virtual XML documents for relational data via an XML schema which is transformed from the underlying relational database schema such that users can access the relational database through the XML schema. In this paper, we discuss issues in transforming a relational database schema into the corresponding XML schema. We aim to preserve all integrity constraints defined in a relational database schema, to achieve high level of nesting and to avoid introducing data redundancy in the transformed XML schema. In the paper, we first propose a basic transformation algorithm which introduces no data redundancy, then we improve the algorithm by exploring further nesting of the transformed XML schema.     

XML文档加密和签名的研究与实现

针对普通XML文档的机密性和完整性需求,首先介绍了XML文档加密与签名的原理和语法结构,然后研究了XML文档加密与签名的类型,在此基础上用java语言实现XML文档的加密和数字签名,最后提出了XML文档的安全交换模型。实验表明,该方法能够有效地确保XML文档的机密性和完整性,是实现XML文档安全交换的一种很有发展前景的保障技术。     

基于XML数据集成与交换中的完整性约束研究

介绍了CoXML系统中提出的3种新的XML完整性约束技术:基于XML的数据交换中的函数依赖转换方法,面向XML Schema的键约束转换方法和基于XPath的XML文档键约束验证方法,并且通过CoXML系统的实现验证了这些技术的有效性.