| XML
Extensible Markup Language or XML (http://www.w3.org/TR/REC-xml/)
appeared as a recommendation of the World Wide Web Consortium
(http://www.w3.org)
in early 1998. XML is a restricted subset of Standard
Generalized Markup Language or SGML (ISO/IEC 8879). By some
grace, XML has enjoyed considerable popularity and has been
almost universally received as an interoperability solution
for heterogeneous computer systems. Although not without
shortcomings, XML is probably the best thing we have going for
us to deal with software interoperability issues, mainly
because of its wide acceptance and presence.
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Today, you can find XML just about
anywhere you find software. To name a few examples:
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OpenOffice's file format consists
of a set of ZIP-archived XML files.
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Ant's build file format is written
in XML, as are Microsoft Visual Studio .NET project
files (http://msdn.microsoft.com/vstudio/).
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Mac plist configuration files are
also written in XML.
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Web pages now increasingly use
Extensible Hypertext Markup Language (XHTML), an XML
version of HTML.
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XML User Interface Language (XUL)
is a Mozilla project that allows you to define
applications with XML (http://www.mozilla.org/projects/xul/).
Likewise, Extensible Application Markup Language
(XAML) is an XML-based language for defining user
interfaces for the Avalon framework, part of
Microsoft's upcoming release of Windows code-named
"Longhorn" (http://msdn.microsoft.com/longhorn/).
XML is by no means a panacea for all
the ills of interchange, but it's becoming an
increasingly practical option for packaging and moving
data in and out of systems or for representing data in a
consistent, readable way. And it can be fun to use, too,
as many of the hacks in this book demonstrate. |
The XML specification defines a syntax for
creating markup. Markup consists of elements,
attributes, and other structures that allow you to label
documents and data in a way that can give them meaning that
other human beings or software can understand and interpret.
Because reliable XML parsers are readily and often freely
available in a variety of programming languages, it is
relatively easy to integrate XML processing into just about
any application. >> Next
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