XML is all about metadata and the idea that certain groups of people have similar needs for describing and organizing the data they use. Like HTML, XML is a set of tags and declarations -- but rather than being concerned with formatting information on a page, XML focuses on providing information about the data itself and how it relates to other data.

Describes XML categories, XML document types and how to create them, the XML DTD, XML elements and attributes providing many examples.

XML's usage is continuing to grow quickly as both individuals and companies realize its potential. However, in many ways XML is still a relatively new technology, and many people, possibly you, are just now learning what it can do for them. Unlike some other software technologies such as HTML or even Java, XML is a little fuzzier in terms of how it is applied in different scenarios. Just as it's difficult to look at a person and grasp how their DNA makes them who they are, it can also be challenging to look at an application and get a grasp for how XML fits into the equation. This tutorial introduces you to XML and gives you some insight as to why it was created and what it can do.

XSL Formatting Objects (XSL-FO) are the second half of the Extensible Stylesheet Language (XSL). XSL-FO is an XML application that describes how pages will look when presented to a reader. A style sheet uses the XSL transformation language to transform an XML document in a semantic vocabulary into a new XML document that uses the XSL-FO presentational vocabulary. While one can hope that Web browsers will one day know how to directly display data marked up with XSL formatting objects, for now an additional step is necessary in which the output document is further transformed into some other format, such as Adobe's PDF.

XML stands for (Extensible Markup Language)which is a simplified subset of the Standard Generalized Markup Language (SGML) which provides a file format for representing data, a schema for describing data structure, and a mechanism for extending and annotating HTML with semantic information.

XPointer, the XML Pointer Language, defines an addressing scheme for individual parts of an XML document. These addresses can be used by any application that needs to identify parts of or locations in an XML document. For instance, an XML editor could use an XPointer to identify the current position of the insertion point or the range of the selection. An XInclude processor can use an XPointer to determine what part of a document to include. And the URI in an XLink can include an XPointer fragment identifier that locates one particular element in the targeted document. XPointers use the same XPath syntax that you're familiar with from XSL transformations to identify the parts of the document they point to, along with a few additional pieces.

This free book is an excellent tutorial book for beginners. It is a collection of notes and sample codes written by the author while he was learning XML and related technologies. Topics include DOM, DTD, J2SDK, Java, SAX, Syntax, Templates, XML, XPath, XSD, XSL, XSLT, XSL-FO.

Linking in XML is divided into two parts, XLink and XPointers. XLink, the XML Linking Language, defines how one document links to another document. XPointer, the XML Pointer Language, defines how individual parts of a document are addressed. An XLink points to a URI (in practice, a URL) that specifies a particular resource. This URI may include an XPointer part that more specifically identifies the desired part or section of the targeted resource or document. This paper explores XLinks.