A Query Language for XML

A Query Language for XML

An important application of XML is the interchange of electronic data (EDI) between multiple data sources on the Web. As XML data proliferates on the Web, applications will need to integrate and aggregate data from multiple source and clean and transform data to facilitate exchange. Data extraction, conversion, transformation, and integration are all well-understood database problems, and their solutions rely on a query language. We present a query language for XML, called XML-QL, which we argue is suitable for performing the above tasks. XML-QL is a declarative, ``relational complete'' query language and is simple enough that it can be optimized. XML-QL can extract data from existing XML documents and construct new XML documents.

Keywords: XML, query languages, electronic-data interchange (EDI)

Introduction
The goal of XML is to provide many of SGML's benefits not available in HTML and to provide them in a language that is easier to learn and use than complete SGML. These benefits include user-defined tags, nested elements, and an optional validation of document structure with respect to a Document Type Descriptor (DTD).

One important application of XML is the interchange of electronic data (EDI) between two or more data sources on the Web. Electronic data is primarily intended for computer, not human, consumption. For example, search robots could integrate automatically information from related sources that publish their data in XML format, e.g., stock quotes from financial sites, sports scores from news sites; businesses could publish data about their products and services, and potential customers could compare and process this information automatically; and business partners could exchange internal operational data between their information systems on secure channels. New opportunities will arise for third parties to add value by integrating, transforming, cleaning, and aggregating XML data. In this paper, we focus on XML's application to EDI. Specifically, we take a database view, as opposed to document view, of XML. We consider an XML document to be a database and a DTD to be a database schema.

Click to Read More/Download

DocBook: The Definitive Guide By Norman Walsh & Leonard Muellner

DocBook: The Definitive Guide

By Norman Walsh & Leonard Muellner

This book is designed to be the clear, concise, normative reference to the DocBook DTD. This book is the official documentation for the DocBook DTD.

We hope to answer, definitively, all the questions you might have about all the elements and entities in DocBook. In particular, we cover the following subjects:

• The general nature of DocBook. With over 300 elements, DocBook can be a bit overwhelming at first. We quickly get you up to speed on how the pieces fit together.
• How to write DocBook documents. Where should you start and what should you do?
• Parsing and validation. After you've written a document, how can you tell if it really conforms to the DocBook DTD?
• How to publish DocBook documents. After you've written one, what do you do with it? We provide a guide to using some popular free tools to publish DocBook documents both in print and on the Web.
• Customizing the DTD. Many individuals and corporations have standardized on the DocBook DTD. Whether your subject matter is computer software documentation or not, we explain how you can write a "customization layer" to tailor DocBook explicitly for your information.
• Understanding all of the elements. Each element is extensively documented, including the intended semantics and the purpose of all its attributes. An example of proper usage is given for every element. The parameter entities and character entities are also described.
  Stylesheets. Several standard stylesheet languages are briefly described.
• XML compatability. We outline all of the points that you'll need to consider as you or your organization contemplate XML for authoring, publishing, or both.
• Additional resources and a CD-ROM. Finally, we direct you to other places you can go for all the latest info, and offer a complete set of online documentation on the CD-ROM.

We expect that most readers will have some familiarity with SGML or XML. Even if your experience goes no farther than writing a few HTML pages, you're probably in good shape. Although we provide an introduction to SGML, XML, and structured markup, this book may not suffice as your only tutorial about SGML and XML. This depends, naturally, on your needs and experience. For a list of some other good resources, consult Appendix D.

Some sections of this book describe tools and applications. For the most part, these are Microsoft Windows or UNIX applications, although there's nothing about DocBook that makes it unsuitable for the Mac or VM/CMS or any other operating system of your choice.

Click to Read More

Extensible Markup Language (XML)

Extensible Markup Language (XML)

Extensible Markup Language (XML) is a simple, very flexible text format derived from SGML (ISO 8879). Originally designed to meet the challenges of large-scale electronic publishing, XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere.

This page describes the work being done at W3C within the XML Activity, and how it is structured. Work at W3C takes place in Working Groups. The Working Groups within the XML Activity are listed below, together with links to their individual web pages.

You can find and download formal technical specifications here, because we publish them. This is not a place to find tutorials, products, courses, books or other XML-related information. There are some links below that may help you find such resources.

You will find links to W3C Recommendations, Proposed Recommendations, Working Drafts, conformance test suites and other documents on the pages for each Working Group. Each document also contains email addresses you can use to send comments or questions, for example if you have been writing software to implement them and have found problems or errors.

Click to Read More

Ground Zero XML Tutorial

Ground Zero XML Tutorial

XML in relation to Markup Languages
This manual is intended for users with no previous experience in web publishing. We must therefore assume that if you read this, you have no experience with areas such as HTML, Java or Cgi. Not to worry. You don't need to have any experience from HTML to learn XML. The one advantage you have if you know something about HTML already is that most textbooks teach XML in a way that relies heavily on pointing out the differences between the two languages. This is not so strange considering that HTML and XML are "siblings" in the sense that they are derived from the same "parent" language: SGML. This leads us to our angle on this manual. Instead of comparing XML to HTML, we will try to see XML in relation to markup languages in general and how this can be a worthwhile addition to the World Wide Web.

What is Markup ?
This brings us to our first item on the agenda: what exactly is a markup language? In the more general sense of the term, it is by no means a new word. It has been used for quite some time in the print and design world as a means for the author/publisher of a text to highlight sections that have some sort of special structural or contextual meaning. This could be anything from individual words that carry a special meaning or simply an indication of where one chapter ends and another one starts. The tradition of marking up texts goes all the way back to the time when scribes wrote their comments in the margins around the edge of the manuscript, or used different inks to make certain words stand out from the rest of the text.

Click to Read More

Introduction to XML

Introduction to XML

XML was designed to describe data and to focus on what data is. HTML was designed to display data and to focus on how data looks.

What You Should Already Know
Before you continue you should have a basic understanding of the following:

• HTML / XHTML
• JavaScript or VBScript

What is XML?

• XML stands for EXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to describe data
• XML tags are not predefined. You must define your own tags
• XML uses a Document Type Definition (DTD) or an XML Schema to describe the data
• XML with a DTD or XML Schema is designed to be self-descriptive
• XML is a W3C Recommendation

Click to Read More

Introduction to XML for web developers

Introduction to XML for web developers

Introduction to XML for Web Developers is a four-part course designed by Selena Sol. Other tutorials are available at Web Ware.

What is XML 

Like HTML, XML (also known as Extensible Markup Language) is a markup language which relies on the concept of rule-specifying tags and the use of a tag-processing application that knows how to deal with the tags.

"The correct title of this specification, and the correct full name of XML, is "Extensible Markup Language". "eXtensible Markup Language" is just a spelling error. However, the abbreviation "XML" is not only correct but, appearing as it does in the title of the specification, an official name of the Extensible Markup Language.

The name and abbreviation were invented by James Clark; other options under consideration had included MGML, (Minimal Generalized Markup Language), MAGMA (Minimal Architecture For Generalized Markup Applications), and SLIM (Structured Language for Internet Markup)" - Extensible Markup Language (XML) 1.0 Specs, The Annotated Version.

Click to Read More

Extensible Markup Language (XML) 1.0

Extensible Markup Language (XML) 1.0

W3C Recommendation 10-February-1998

Abstract

The Extensible Markup Language (XML) is a subset of SGML that is completely described in this document. Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML has been designed for ease of implementation and for interoperability with both SGML and HTML.

Status of this document

This document has been reviewed by W3C Members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web...

Click to Read More

Processing XML with Java By Elliotte Rusty Harold

Processing XML with Java

By Elliotte Rusty Harold

Welcome to Processing XML with Java, a complete tutorial about writing Java programs that read and write XML documents. This is the most comprehensive and up-to-date book about integrating XML with Java (and vice versa) you can buy. It contains over 1000 pages of detailed information on SAX, DOM, JDOM, JAXP, TrAX, XPath, XSLT, SOAP, and lots of other juicy acronyms. This book is written for Java programmers who want to learn how to read and write XML documents from their code. The paper version is published by Addison-Wesley, and can be found at fine bookstores everywhere including Amazon and Barnes & Noble. The list price is $54.95, but most bookstores are offering their usual discounts...

This book is written for experienced Java programmers who want to integrate XML into their systems. Java is the ideal language for processing XML documents. Its strong Unicode support in particular made it the preferred language for many early implementers. Consequently, more XML tools have been written in Java than in any other language. More open source XML tools are written in Java than in any other language. More programmers process XML in Java than in any other language.

Processing XML with Java will teach you how to:

• Save XML documents from applications written in Java
• Read XML documents produced by other programs
• Search, query, and update XML documents
• Convert legacy flat data into hierarchical XML
• Communicate with network servers that send and receive XML data
• Validate documents against DTDs, schemas, and business rules
• Combine functional XSLT transforms with traditional imperative Java code

This book is meant for Java programmers who need to do anything with XML. It teaches the fundamentals and advanced topics, leaving nothing out. It is a comprehensive course in processing XML with Java that takes developers from little knowledge of XML to designing sophisticated XML applications and parsing complicated documents. The examples cover a wide range of possible uses including file formats, data exchange, document transformation, database integration, and more.

Click to Read More

The XML Files: Using XML for Business-to-Business and Business-to-Consumer Applications

The XML Files: Using XML for Business-to-Business and Business-to-Consumer Applications

When you get right down to it, e-business is a simple concept. An e-business is an organization that connects critical business systems directly to key actors such as customers, employees, suppliers, and distributors, by using Internet technology. But this simple concept quickly becomes powerful. As customers, employees, suppliers and distributors are all connected to the business systems and information they need, e-business actually transforms key business processes. This book intends to present the emergence, and the impacts of the Extensible Markup Language (XML) in e-business world.

By reading this book, customers, IBM sales people, IT architects, and IT specialists will have the opportunity to understand how the “marriage” between XML technology and the IBM Application Framework for e-business can help to leverage e-business applications, particularly those based on business-to-business (B2B), and business-to-consumer (B2C) models.

In writing this book, residents had many discussions with IBM people involved in e-business, XML, and related technologies. They also “surfed the net” (IBM and non-IBM) to gather information about the e-business world in general, the IBM e-business vision and solution, and the XML technology applied to the e-business applications.

This book is designed to expand your knowledge on the following topics:

• The e-business market: what is going on, trends, and directions.
• The added value of XML technology to help to solve issues, and some challenges that arise through e-business applications such as data exchange, portal services, and pervasive device support.
• How IBM cuts XML and related technologies down to size in its application Framework for e-business, including details of the IBM offering in terms of architecture and tools to design, develop, deploy, and run complex B2B models (applications sharing services among different trading partners), and B2C models (applications providing end-users with various services).

This book also depicts a case study in the eMarketPlace field that demonstrates the ability of XML technology combined with the IBM Application Framework for e-business to implement both B2B and B2C models.

Click to Read More

Transferring data between XML documents and relational databases By Ronald Bourret

Transferring data between XML documents and relational databases

By Ronald Bourret

In this paper we will discuss strategies for transferring data between XML documents and relational databases according to two mappings (a table-based mapping and an object-based mapping) commonly used to map DTDs to relational databases. Although the discussion largely focuses on the difference between using SAX- and DOM-based tools to transfer data, it also discusses a number of strategies for traversing both the XML and database hierarchies and the tradeoffs among them.

IMPORTANT: The table-based mapping and the object-based mapping are not discussed in this paper. However, you must understand them before reading this paper. For more information, see Mapping DTDs to Databases.

Click to Read More

Softsteel WML Tutorial

Softsteel WML Tutorial

This tutorial takes you through the basics of WAP, and provides all the information you need to create your own WAP pages using the Wireless Markup Language (WML). The WMLScript tutorial that we promised has unfortunately had to be postponed, however. We shall return to it when we have time.

Introduction to WAP
At the time of writing, the backlash against the mobile Internet is going strong. This is in major part a response to the massive hype that accompanied the first WAP-enabled handsets in 1999-2000. Whilst these devices were marketed as windows onto the Internet, their limitations soon became obvious. Not only were they unable to show most Internet content, with little content of their own, they were also very slow to connect and navigate.

This backlash is itself a creature of hype, however; as out of touch as the original euphoria. In a world grown accustomed to the capabilities of the wired Internet, it is easy to forget that the mobile Internet is still at a very early stage of development. In the next five years we will see much faster, 'always-on' networks. We will also see a range of functions taking advantage of browser location-awareness, providing services tailored just for portables. So, the mobile Internet is going to have a strong future. And - as with the wired Internet - the most successful developers will be those who get in early, ahead of the crowd...

Click to Read More

XML and Databases By Ronald Bourret

XML and Databases

By Ronald Bourret

This paper gives a high-level overview of how to use XML with databases. It describes how the differences between data-centric and document-centric documents affect their usage with databases, how XML is commonly used with relational databases, and what native XML databases are and when to use them.

NOTE: Although the information discussed in this paper is (mostly) up-to-date, the idea that the world of XML and databases can be seen through the data-centric/document-centric divide is somewhat dated. At the time this paper was originally written (1999), it was a convenient metaphor for introducing native XML databases, which were then not widely understood, even in the database community. However, it was always somewhat unrealistic, as many XML documents are not strictly data-centric or document-centric, but somewhere in between. So while the data-centric/document-centric divide is a convenient starting point, it is better to understand the differences between XML-enabled databases and native XML databases and to choose the appropriate database based on your processing needs. For a more modern look at the difference between XML-enabled and native XML databases, see chapter 1 of XML for DB2 Information Integration.

Click to Read More

XML for DB2 Information Integration

XML for DB2 Information Integration

In many organizations, relational databases are the backbone for data storage and retrieval. Over the last couple of years, XML has become the de facto standard to exchange information between organizations, as well as between departments or applications within the same organization. Since data tends to live in databases, it needs to be converted from a relational format into an XML format when involved in those data exchanges, as well as converted (back) from XML into a relational format for storage, or for handling by other applications.

How can we achieve this? This IBM Redbook describes how to design the mapping between XML and relational data, and vice versa, to enable a flexible exchange of information.

IBM provides a number of products to help you bridge the gap between XML and its relational database, DB2. The DB2 engine itself provides support to generate XML fragments from relational data through the use of SQL/XML built-in functions. DB2 also provides the DB2 XML Extender. It allows you to perform XML composition, like SQL/XML, but also provides functionality to decompose XML documents and store XML documents intact inside the database. XML Extender also provides a set of transformation and validation functions. Another option to work with XML is to use the XML wrapper, a part of the set of non-relational wrappers of DB2 Information Integrator. This redbook also looks at the IBM tools available to assist you when dealing with XML, specifically WebSphere Application Developer and DB2 Control Center.To add a more practical angle, these functions and products are illustrated through the development of a simple application.

Click to Read More/Download

XML Certification Tutorial By Vibha Verma

XML Certification Tutorial

By Vibha Verma

With XMLs popularity, and close relation between XML and Java, IBMs certification for XML is becoming popular. We offer now a tutorial on XML for IBM certification. This tutorial has been written by Vibha Verma. We are thankful to Vibha for making her notes available for Javaprepare readers.

This tutorial highlights important concepts that you must know for IBM's XML Certification exam. Read the tutorial when you have grasped the fundamentals of the XML technology and want to prepare for the Certification exam....

Click to Read More

XML - Free Chapters

XML - Free Chapters

Here we are providing some links for XML books free chapters from O'Reily, Wrox Press and from some other publishers.

Free Chapters are from following books

• XML in a Nutshell
• Java and XML
• Java Examples in a Nutshell
• Learning XML
• Professional XML
• Professional Java XML Programming with Servlets and JSP
• Designing Distributed Applications with XML, ASP, IE5, LDAP and MSMQ
• Building Oracle XML Applications
• The XML Bible, 2nd edition
• XML How to Program

Various Links for downloading

• XPath
• Web Publishing Frameworks
• XML
• Markup and Core Concepts
• SAX 1.0: The Simple API for XML
• JavaBeans Components in JSP Pages
• What is Metadata
• Transforming XML with XSLT and ASP
• XSL Transformations
• XSL Formatting Objects
• XLinks
• XPointers
• Schemas
• Document Type Definition (DTD)
• XML Path Language (XPath)
• XSL: Extensible Stylesheet Language Formatting Objects
• Custom Markup Languages: Part I

XQL (XML Query Language) By Jonathan Robie

XQL (XML Query Language)

By Jonathan Robie

As more and more information is either stored in XML, exchanged in XML, or presented as XML through various interfaces, the ability to intelligently query our XML data sources becomes increasingly important. XML documents are structured documents – they blur the distinction between data and documents, allowing documents to be treated as data sources, and traditional data sources to be treated as documents.

XQL is a query language designed specifically for XML. In the same sense that SQL is a query language for relational tables and OQL is a query language for objects stored in an object database, XQL is a query language for XML documents. The basic constructs of XQL correspond directly to the basic structures of XML, and XQL is closely related to XPath, the common locator syntax used by XSL and XPointers. Since queries, transformation patterns, and links are all based on patterns in structures found in possible XML documents, a common model for the pattern language used in these three applications is both possible and desirable, and a common syntax to express the patterns expressed by that model simplifies the task of the user who must master a variety of XML-related technologies. Although XQL originated before XSL Patterns, there were strong similarities between the two languages, and we have adopted XPath syntax for the constructs which differed. Not all constructs found in XPath were needed for queries, and some constructs used in XQL are not found in XPath, but the two languages share a common subset.

The XQL language described in this paper contains several features not found in previously published versions of the language, including joins, links, text containment, and extensible functions. These new features are inspired in large part by discussions stemming from the W3C QL '98 Workshop, and make it possible to combine information from heterogeneous data sources in powerful ways. Great care has been made to maintain the fundamental simplicity of XQL while adding these features.

This paper is intended as input for the upcoming W3C Query Language Activity, and for the further development of XPath.

Click to Read More

XML Road Map

XML Road Map

XML, Extensible Markup Language Version 1.0. is a new language for the encoding of structured data on the Web. XML is a simple, very flexible text format derived from SGML (ISO 8879). XML was originally designed to meet the challenges of large-scale electronic publishing. Today XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web.

XML was designed to:

• Enable internationalized media-independent electronic publishing
• Allow industries to define platform-independent protocols for the exchange of data, especially the data of electronic commerce
• Deliver information to user agents in a form that allows automatic processing after receipt
• Make it easier to develop software to handle specialized information distributed over the Web
• Make it easy for people to process data using inexpensive software
• Allow people to display information the way they want it, under stylesheet control
• Make it easier to provide metadata -- data about information -- that will help people find information and help information producers and consumers find each other

Click to Read More

XML Basics - An Introduction to XML by Jan Egil Refsnes

XML Basics - An Introduction to XML

by Jan Egil Refsnes

What is XML?

• XML stands for EXtensible Markup Language
• XML is a markup language much like HTML.
• XML was designed to describe data.
• XML tags are not predefined in XML. You must define your own tags.
• XML is self describing.
• XML uses a DTD (Document Type Definition) to formally describe the data.

The main difference between XML and HTML

• XML is not a replacement for HTML.XML and HTML were designed with different goals:
• XML was designed to describe data and to focus on what data is.HTML was designed to display data and to focus on how data looks.
• HTML is about displaying information, XML is about describing information.

XML is extensible
The tags used to markup HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard.

XML allows the author to define his own tags and his own document structure.

Click to Read More

XSL Concepts and Practical Use

XSL Concepts and Practical Use

What's with stylesheets in the first place?

• XML is not a fixed tag set (like HTML)
• XML by itself has no (application) semantics
• A generic XML processor has no idea what is "meant" by the XML
• XML markup does not (usually) include formatting information
• The information in an XML document may not be in the form in which it is desired to present it
• Therefore there must be something in addition to the XML document that provides information on how to present or otherwise process the XML

Advantages to separating content from style
Contrary to when style information is hard-coded into the content, separation of style from content allows for the same data to be presented in different ways. This enables:

• Reuse of fragments of data: the same content should look different in different contexts
• Multiple output formats: different media (paper, online), different sizes (manuals, reports), different classes of output devices (workstations, hand-held devices)
• Styles tailored to the reader's preference (e.g., accessibility): print size, color, simplified layout for audio readers
• Standardized styles: corporate stylesheets can be applied to the content at any time
• Freedom from style issues for content authors: technical writers needn't be concerned with layout issues because the correct style can be applied later

Click to Read More

XUL Programmer's Reference Manual

XUL Programmer's Reference Manual

This document is a reference for the XML-based User Interface Language (XUL). Like the interface widgets that XUL describes, this reference is organized hierarchically. For example, almost all of the widgets inherit from the box widget, which means that they share the attributes described in that area of the reference. Where attributes are inherited, those attributes are italicized in the spelling for that widget. The menubar object and the attributes it inherits from box are a good example of this.

A very small collection of attributes are general to all widgets but not inherited from generalized widgets or tools like . These include attributes like id, with which every XUL widget can be specified. These attributes are defined in a common file. Where common attributes are implemented or used differently by different widgets, the attributes are described with their respective widgets. Values for class vary quite a bit from widget to widget, for example, so class is defined separately for each widget that includes it.

The following sections contain a very brief introduction to XUL. This introduction is intended merely to preface the XUL reference information that this document contains.

Click to Read More/Download