Buzz about the value and implications of XML has reached an all-time high, with lofty claims of its potential to transform business and society, doing everything from simple document formatting to curing the common cold. I don't recommend you empty your medicine cabinet just yet. However, do take seriously the developments surrounding XML and its associated technologies. While XML might not merit all the hyperbole, it remains useful. Knowing how to apply this simple meta-language can help you create solutions that will give you a strong competitive advantage.
The addition of new values to a list is a common and necessary requirement. Schema designers often seek to build into the architecture a means to permit additional values that were unknown at design time. How can schema designers create an enumerated value list that is extensible and easy to implement? Discover several approaches used to achieve this goal.
There has been much debate over two quite different approaches to implementing XML services. The "web services" approach leverages a rather large and not yet stabilized stack of formats and protocols built on top of SOAP that promise secure, reliable operations; the "REST" or "Plain old XML over HTTP" approach keeps the basic formats and operations quite simple, but puts the burden for any security or end-to-end reliability on the application developer rather than the computing infrastructure. This presentation considers a third approach which complements many of the ideas in both WS and REST but uses an XML-capable DBMS as the messaging hub or service broker. This makes it feasible to support asynchronous, loosely coupled communications between service requesters and providers.
If you're a Java 2 Enterprise Edition (J2EE) developer, you'll want to preview the SQLXML technology, currently in development. Check out procedures to create an XML document, store an XML document in a relational database, retrieve an XML document from a database, and navigate an XML document with the SQLXML Java data type.
Topic Maps provide a very flexible and robust way to add arbitrary data to a relational databases at runtime. Moreover, Topic Maps come with a predefined exchange mechanism (the XML Topic Maps (XTM) interchange syntax) to allow data to be exported to XML.
Design principles for XML schemas that eliminate redundancies and avoid update anomalies have been studied recently. Several normal forms, generalizing those for relational databases, have been proposed. All of them, however, are based on the assumption of a native XML storage, while in practice most of XML data is stored in relational databases. In this paper we study XML design and normalization for relational storage of XML documents. To be able to relate and compare XML and relational designs, we use an information-theoretic framework that measures information content in relations and documents, with higher values corresponding to lower levels of redundancy. We show that most common relational storage schemes preserve the notion of being well-designed (i.e., anomalies- and redundancy-free). Thus, existing XML normal forms guarantee well-designed relational storages as well. We further show that if this perfect option is not achievable, then a slight restriction on XML constraints guarantees a “second-best” relational design, according to possible values of the information-theoretic measure. We ﬁnally consider an edge-based relational representation of XML documents, and show that while it has similar information-theoretic properties with other relational representations, it can behave signiﬁcantly worse in terms of enforcing integrity constraints.
XML has dramatically changed the way we exchange and store data, and a new crop of standards promises to change the way we query data. On today's Internet, most data is queried and stored using relational databases, exchanged as XML, and displayed as HTML. For those who need to use XML and databases together, the last five years have been chaotic, creative, interesting, and often frustrating. Every major database vendor has added XML support, but each vendor takes a very different approach, and sometimes changes that approach dramatically from one version to the next. Today, the vendors seem to be lining up behind XQuery and the SQL/XML mappings - is this just the latest wave of marketing hype, or has the industry now found its way?
Relational database systems (and the related standards body ANSI/INCITS H2) are busy adding XML support. One of the main components of such XML extensions will be support for the upcoming XML query language XQuery. The presentation will outline how XQuery and XML conceptually fit into a relational database environment. It will cover the organization of the XML in the database, how to type it using W3C XML Schema, how to query it both in conjunction with SQL and using top-level XQuery. It will present the concepts, talk about new developments in the ISO/ANSI SQL/XML standards and present some demos of XQuery in the upcoming Microsoft® SQL Server 2005.
XQuery speeds up the process of finding information contained in an XML document -- which is very handy when dealing with long XML documents. This article, the second of two parts, will teach you how to write XQuery expressions.