XML Benchmarking

Since XML technologies have become a standard for data representation, numerous methods for processing XML data emerge every day. Consequently, it is necessary to compare the newly proposed methods with the existing ones, as well as analyze the effect of a particular method when applied to various types of data. In this chapter, the auhtors provide an overview of existing approaches to XML benchmarking from the perspective of various applications and show that to date the problem has been highly marginalized. Therefore, in the second part of the chapter they discuss persisting open issues and their possible solutions.

Modeling XML Warehouses for Complex Data

Current data warehouses deal for the most part with numerical data. However, decision makers need to analyze data presented in all formats which one can qualify as complex data. Warehousing complex data is a new challenge for the scientific community. Indeed, it requires revisiting the whole warehousing process in order to take into account the complex structure of data; therefore, many concepts of data warehousing will need to be redefined. In particular, modeling complex data in a unique format for analysis purposes is a challenge. In this chapter, the authors present a complex data warehouse model at both conceptual and logical levels. They show how XML is suitable for capturing the main concepts of their model, and present the main issues related to these data warehouses.

Issues in Personalized Access to Multi-Version XML Documents

In several application fields including legal and medical domains, XML documents are “versioned” along different dimensions of interest, whose nature depends on the application needs such as time, space and security. Specifically, temporal and Semantic versioning is particularly demanding in a broad range of application domains where temporal versioning can be used to maintain histories of the underlying resources along various time dimensions, and Semantic versioning can then be used to model limited applicability of resources to individual cases or contexts. The selection and reconstruction of the version(s) of interest for a user means the retrieval of those fragments of documents that match both the implicit and explicit user needs, which can be formalized as what we call personalization queries. In this chapter, the authors focus on the design and implementation issues of a personalization query processor. They consider different design options and, among them, they introduce an in-depth study of a native solution by showing, also through experimental evaluation, how some of the best performing technological solutions available today for XML data management can be successfully extended and optimally combined in order to support personalization queries.

Data Integration Issues and Opportunities in Biological XML Data Management

There is a proliferation of research and industrial organizations that produce sources of huge amounts of biological data issuing from experimentation with biological systems. In order to make these heterogeneous data sources easy to use, several efforts at data integration are currently being undertaken based mainly on XML. Starting from a discussion of the main biological data types and system interactions that need to be represented, the authors deal with the main approaches proposed for their modelling through XML. Then, they show the current efforts in biological data integration and how an increasing amount of Semantic information is required in terms of vocabulary control and ontologies. Finally, future research directions in biological data integration are discussed.

Security Issues in Outsourced XML Databases

In an outsourced XML database service model, organizations rely upon the premises of external service providers for the storage and retrieval management of their XML data. Since, typically, service providers are not fully trusted; this model introduces numerous interesting research challenges. Among them, the most crucial security research questions relate to data confidentiality, user and data privacy, queryassurance, secure auditing, and secure and efficient storage model. Although there exists a large number of related research works on these topics, the authors are still at the initial stage and the research results are still far from practical maturity. In this chapter, they extensively discuss all potential security issues mentioned above and the existing solutions, and present open research issues relevant to security requirements in outsourced XML databases.

Native XML Programming

XML engines are usually designed to solve a single class of problems: transformations of XML structures, validations of XML instances, Web publishing, and so forth. As the relevant operations or declarations are described with XML vocabularies, their respective engines have to face similar issues such as unmarshalling, and at runtime data handling. In order to address such issues, the author proposes an innovative and reliable XPath-based framework, active tags, that unifies XML technologies in a coherent system where various XML languages can cooperate. In this chapter’s approach, the authors focus on its type system that enhances the XML Data Model, specifically by allowing XPath expressions to be applied on non-XML objects, and on the ability of the engine to mix declarative languages with imperative constructs. This valuable feature is illustrated with the Active Schema Language, which allows the building of dynamic-content models.

Continuous and Progressive XML Query Processing and its Applications

Since XML technologies have become a standard for data representation, a great amount of discussion has been generated by the persisting open issues and their possible solutions. In this chapter, the authors consider the design space for XML query processing techniques that can handle ad hoc and continuous XPath or XQuery queries over XML data streams. This chapter presents the state-of-art techniques in continuous and progressive XML query processing. They also discuss several open issues and future trends.

XSLT

The widespread usage of XML in the last few years has resulted in the development of a number of XML query languages like XSLT or the later developed XQuery language. Today, there are many products like databases in the area of XML processing that support either XSLT or XQuery, but not both of them. This may prevent users from employing their favourite XML query language. In this chapter, the authors show that both languages have comparable expression power and present a scheme for translating XQuery to XSLT and vice versa. This translation scheme enables a user to employ either XSLT or XQuery for each product which supports one of these languages. They also summarize in this chapter both current and future trends and research issues and also consider those that might emerge in the common area of XSLT and XQuery and which are particular to XSLT.

XML Schema Evolution and Versioning

The large dynamicity of XML documents on the Web has created the need to adequately support structural changes and to account for the possibility of evolving and versioning the schemas describing XML document structures. This chapter discusses and compares the support for schema evolution and versioning provided by commercial systems as well as the most relevant approaches and prototypes proposed and developed by the research community.

Recent Advances and Challenges in XML Document Routing

Content-based routing is a form of data delivery whereby the flow of messages is driven by their content rather than the IP address of their destination. With the recognition of XML as the standard for data exchange, specialized XML routing services become necessary. In this chapter, the authors first demonstrate the relevance of such systems by presenting different world application scenarios where XML routing systems are needed and/or employed. Then, they present a survey of the current state of the art. Lastly, they attempt to identify issues and problems that have yet to be investigated. Their discussion will help identify open problems and issues and suggest directions for further research in the context of such systems.