一种DTDs完全一致性判断算法

一个语法上完全正确的DTD可能是不一致的,即不存在任何“有效的”XML文档遵循这个DTD·不一致的DTDs应当尽可能避免·现已提出的无完整性约束的DTDs一致性判断方法,考虑的都是如何判断整个DTDs是否存在有效的XML文档相对应,忽略了对DTDs结构中不合理的子结构的一致性判断,因此一致性成立的DTDs中仍有可能存在子结构没有相对应的有效XML数据·为解决这一问题,提出了DTDs完全一致性的概念,分析了能够导致DTDs不完全一致性的各种因素,并给出了线性时间复杂性的DTDs完全一致性判断算法·     

基于路径的DTD完全一致性判断和纠错算法

为了解决一致性成立的DTD仍可能存在一致性不成立的子结构问题,设计了新的路径信息表示规则,并给出了一种新的、线性时间复杂度的DTD完全一致性判断和纠错算法。     

一种DTD一致性的判定方法

DTD作为一种XML文档结构的模式语言得到了广泛的使用,它描述了相似的XML文档的结构。DTD的一致性是指对于一个给定的DTD,判断是否存在至少有一个XML文档满足DTD。在引入DTD一致性的形式化定义的基础上,分析了引起DTD不一致性的各种因素,提出了DTD一致性的判定方法。     

DTD模式下的XML结构完整性约束

XML结构完整性约束(XSICs)描述了XML文档中节点或路径之间结构关系,这种约束可以看成是DTDs的扩展和补充.定义了元素排他性包含、必需性包含、路径蕴含、路径同现和路径互斥五种XSICs的语法和语义,研究了如何使用XSICs扩展DTDs,并解决了有DTDs的情况下结构完整性约束的逻辑蕴含问题和一致性问题.     

Clustering DTDs: An Interactive Two-Level Approach

XML（eXtensible Markup Language)is a standard which is widely applied in data representation and data exchange,However,as an important concept of XML,DTD(Document Type Definition)is not taken full advantage in current applications.In this paper,a new method for clustering DTDs is presented.and it can be used in XML document clustering.The two-level method clusters the elements in DTDs and clusters DTDs separately.Element clustering forms the first level and provides element clusters,which are the generalization of relevant elements.DTD clustering utilizes the generalized information and forms the second level in the whole clustering process.The two-level method has the following advantages:1) It takes into consideration both the content and the structure within DTDs;2) The generalized information about elements is more useful than the separated words in the vector model;3) The two-level method facilitates the searching of outliers.The experiments show that this method is able to categorize the relevant DTDs effectively.     

DTD约束下的树模式查询的一致性判断

树模式查询被广泛地应用XML数据查询中。树模式查询的一致性判断可以避免不必要的计算,节省查询时间,从而提高查询效率。给出了查询一致性的定义,基于子路径的概念,提出文档类型定义(DTD)约束下的树模式查询的一致性判断算法,并对算法的时间复杂度进行了分析。通过分析比较,该算法是有效的。     

用于XML模式和DTD规范化设计的层次模式设计

XML模式和DTD(document type definition)规范化设计是给出一个很好地表示数据间依赖关系并消除了冗余的XML模式或DTD的集合.目前在这一方面开展的研究还不多,而且才刚起步.Provost提出将关系数据库理论应用于XML模式规范化设计的思想,这一思想还没有付诸实施.在Provost思想的基础上给出用于XML模式和DTD规范化设计的层次模式设计的算法.首先分析了基于Provost思想的层次分解;然后给出用于消除冗余模式的分解树设计算法;最后给出用于XML模式和DTD规范化设计的层次     

XML环的定义、分类、判定和消除

在关系数据库中,无环数据库模式设计是数据库理论与图论相结合而产生的一个新的研究领域.这里的环指的是在关系数据库中由于某些属性存在二义性,使得在查询这些属性的时候存在两条或两条以上的路径,这就形成了环.同样的,在XML文档中也存在着环.为了研究XML文档中的环,基于DTD提出了XML环的概念,分析了存在环结构的DTD,并对XML环进行了分类,给出XML环的判定算法,最后提出了消除XML环的方法.     

用于XML模式和DTD设计的层次分解

对于XML模式和DTD规范化设计,现在开展的研究不多,而且才刚起步。W.Provost提出将关系数据库理论应用于XML模式规范化设计的思想,这一思想还没有付诸实施。该文给出表示XML模式和DTD的层次模式和用于XML模式和DTD规范化设计的层次分解过程,并对产生的层次模式进行分析。在算法产生的层次模式中,完全MVD和嵌入MVD的集合由给出的MVD集合导出。     

存在多值依赖的XML DTD规范化研究

XML DTD文档中可能包含由非函数依赖引起的数据冗余和操作异常,首先从消除DTD文档内数据冗余的角度出发研究了文档的规范化的问题,讨论了在DTD文档中存在多值依赖的情况下,如何规范XML文档,提出了以DTD为模式的XML文档的多值依赖的概念。然后基于多值依赖的概念,提出了XML文档的一种多值依赖范式MXNF。最后在此基础上提出了把一个XML文档的DTD无损联接地分解成为符合MXNF的规范化算法,来规范存在多值依赖的XML DTD文档,并给出了该算法的分析说明。     

A practical approach to extracting DTD-conforming XML documents from heterogeneous data sources

XML documents are becoming popular for business process integration. To achieve interoperability between applications, XML documents must also conform to various commonly used data type definitions (DTDs). However, most business data are not maintained as XML documents. They are stored in various native formats, such as database tables or LDAP directories. Hence, a middleware is needed to dynamically generate XML documents conforming to predefined DTDs from various data sources. As industrial consortia and large corporations have created various DTDs, it is both challenging and time-consuming to design the necessary middleware to conform to so many different DTDs. This problem is particularly acute for a small- or medium-sized enterprise because it lacks the IT skills to quickly develop such a middleware. In this paper, we present XLE, an XML Lightweight Extractor, as a practical approach to dynamically extracting DTD-conforming XML documents from heterogeneous data sources. XLE is based on a framework called DTD source annotation (DTDSA). It treats a DTD as the control structure of a program. The annotations become the program statements, such as functions and assignments. DTD-conforming XML documents are generated by parsing annotated DTDs. Basically, DTD annotations describe declaratively the mappings between target XML documents and the source data. The XLE engine implements a few basic annotations, providing a practical solution for many small- and medium-sized enterprises. However, XLE is designed to be versatile. It allows sophisticated users to plug in their own implementations to access new types of data or to achieve better performance. Heterogeneous data sources can be simply specified in the annotations. A GUI tool is provided to highlight the places where annotations are needed.     

Foundations of Fast Communication via XML

Communication with XML often involves pre-agreed document types. In this paper, we propose an offline parser generation approach to enhance online processing performance for documents conforming to a given DTD. Our examination of DTDs and the languages they define demonstrates the existence of ambiguities. We present an algorithm that maps DTDs to deterministic context-free grammars defining the same languages. We prove the grammars to be LL(1) and LALR(1), making them suitable for standard parser generators. Our experiments show the superior performance of generated optimized parsers. Our results generalize from DTDs to XML schema specifications with certain restrictions, most notably the absence of namespaces, which exceed the scope of context-free grammars.     

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.     

Slicing XML Documents

Program slicing is a well-known technique to extract the program statements that (potentially) affect the values computed at some point of interest. In this work, we introduce a novel slicing method for XML documents. Essentially, given an XML document (which is valid w.r.t. some DTD), we produce a new XML document (a slice) that contains the relevant information in the original XML document according to some criterion. Furthermore, we also output a new DTD such that the computed slice is valid w.r.t. this DTD. A prototype implementation of the XML slicer has been undertaken.