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* NEWS doc/*.xsl doc/*.html: updated the web site separated developers from common pages, made the transition to XHTML1, added validity checking to the makefile rules. Daniel
46 lines
7.1 KiB
HTML
46 lines
7.1 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css">
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TD {font-family: Verdana,Arial,Helvetica}
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BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
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H1 {font-family: Verdana,Arial,Helvetica}
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H2 {font-family: Verdana,Arial,Helvetica}
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H3 {font-family: Verdana,Arial,Helvetica}
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A:link, A:visited, A:active { text-decoration: underline }
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</style><title>Namespaces</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C library for Gnome</h1><h2>Namespaces</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html">Home</a></li><li><a href="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html">Developer Documentation</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="help.html">How to help</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="news.html">News</a></li><li><a href="XMLinfo.html">XML</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="xmldtd.html">Validation & DTDs</a></li><li><a href="encoding.html">Encodings support</a></li><li><a href="catalog.html">Catalog support</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="contribs.html">Contributions</a></li><li><a href="guidelines.html">XML Guidelines</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>The libxml library implements <a href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
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recognizing namespace constructs in the input, and does namespace lookup
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automatically when building the DOM tree. A namespace declaration is
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associated with an in-memory structure and all elements or attributes within
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that namespace point to it. Hence testing the namespace is a simple and fast
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equality operation at the user level.</p><p>I suggest that people using libxml use a namespace, and declare it in the
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root element of their document as the default namespace. Then they don't need
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to use the prefix in the content but we will have a basis for future semantic
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refinement and merging of data from different sources. This doesn't increase
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the size of the XML output significantly, but significantly increases its
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value in the long-term. Example:</p><pre><mydoc xmlns="http://mydoc.example.org/schemas/">
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<elem1>...</elem1>
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<elem2>...</elem2>
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</mydoc></pre><p>The namespace value has to be an absolute URL, but the URL doesn't have to
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point to any existing resource on the Web. It will bind all the element and
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attributes with that URL. I suggest to use an URL within a domain you
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control, and that the URL should contain some kind of version information if
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possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a
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good namespace scheme.</p><p>Then when you load a file, make sure that a namespace carrying the
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version-independent prefix is installed on the root element of your document,
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and if the version information don't match something you know, warn the user
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and be liberal in what you accept as the input. Also do *not* try to base
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namespace checking on the prefix value. <foo:text> may be exactly the
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same as <bar:text> in another document. What really matters is the URI
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associated with the element or the attribute, not the prefix string (which is
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just a shortcut for the full URI). In libxml, element and attributes have an
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<code>ns</code> field pointing to an xmlNs structure detailing the namespace
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prefix and its URI.</p><p>@@Interfaces@@</p><p>@@Examples@@</p><p>Usually people object to using namespaces together with validity checking.
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I will try to make sure that using namespaces won't break validity checking,
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so even if you plan to use or currently are using validation I strongly
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suggest adding namespaces to your document. A default namespace scheme
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<code>xmlns="http://...."</code> should not break validity even on less
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flexible parsers. Using namespaces to mix and differentiate content coming
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from multiple DTDs will certainly break current validation schemes. I will
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try to provide ways to do this, but this may not be portable or
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standardized.</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>
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