Datasheet

16
Part I ✦ Introducing XML
Among other things, an XML document may contain hypertext links to other docu-
ments and resources. These links are created according to the XLink specification.
XLinks identify the documents that they’re linking to with URIs (in theory) or URLs
(in practice). An XLink may further specify the individual part of a document it’s
linking to. These parts are addressed via XPointers.
If an XML document is intended to be read by human beings— and not all XML
documents are— a style sheet provides instructions about how individual elements
are formatted. The style sheet may be written in any of several style sheet languages.
CSS and XSL are the two most popular style sheet languages, and the two best
suited to use with XML.
Summary
In this chapter, you’ve seen a high-level overview of what XML is and what it can do
for you. In particular, you learned the following:
✦ XML is a meta-markup language that enables the creation of markup languages
for particular documents and domains.
✦ XML tags describe the structure and semantics of a document’s content, not
the format of the content. The format is described in a separate style sheet.
✦ XML documents are created in an editor, read by a parser, and displayed by a
browser.
✦ XML on the Web rests on the foundations provided by HTML, CSS, and URLs.
✦ Numerous supporting technologies layer on top of XML, including XSL style
sheets, XLinks, and XPointers. These let you do more than you can accomplish
with just CSS and URLs.
The next chapter presents a number of XML applications that demonstrate the ways
that XML is being used in the real world. Examples include vector graphics, musical
notation, mathematics, chemistry, human resources, and more.
✦✦✦
03 549863 Ch01.qxd 1/28/04 9:46 AM Page 16