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https://github.com/darlinghq/darling-libxml2.git
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123 lines
7.2 KiB
HTML
123 lines
7.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
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<html>
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<head>
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<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">
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<style type="text/css"><!--
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TD {font-size: 10pt; font-family: Verdana,Arial,Helvetica}
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BODY {font-size: 10pt; font-family: Verdana,Arial,Helvetica; margin-top: 5pt; margin-left: 0pt; margin-right: 0pt}
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H1 {font-size: 16pt; font-family: Verdana,Arial,Helvetica}
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H2 {font-size: 14pt; font-family: Verdana,Arial,Helvetica}
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H3 {font-size: 12pt; font-family: Verdana,Arial,Helvetica}
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A:link, A:visited, A:active { text-decoration: underline }
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--></style>
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<title>Namespaces</title>
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</head>
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<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
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<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
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<td width="180">
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<a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome 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>
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</td>
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<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">
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<h1>The XML C library for Gnome</h1>
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<h2>Namespaces</h2>
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</td></tr></table></td></tr></table></td>
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</tr></table>
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<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>
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<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
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<table width="100%" border="0" cellspacing="1" cellpadding="3">
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<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
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<tr><td bgcolor="#fffacd"><ul style="margin-left: -2pt">
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<li><a href="index.html">Home</a></li>
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<li><a href="intro.html">Introduction</a></li>
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<li><a href="FAQ.html">FAQ</a></li>
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<li><a href="docs.html">Documentation</a></li>
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<li><a href="bugs.html">Reporting bugs and getting help</a></li>
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<li><a href="help.html">How to help</a></li>
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<li><a href="downloads.html">Downloads</a></li>
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<li><a href="news.html">News</a></li>
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<li><a href="XML.html">XML</a></li>
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<li><a href="XSLT.html">XSLT</a></li>
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<li><a href="architecture.html">libxml architecture</a></li>
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<li><a href="tree.html">The tree output</a></li>
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<li><a href="interface.html">The SAX interface</a></li>
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<li><a href="xmldtd.html">Validation & DTDs</a></li>
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<li><a href="xmlmem.html">Memory Management</a></li>
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<li><a href="encoding.html">Encodings support</a></li>
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<li><a href="xmlio.html">I/O Interfaces</a></li>
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<li><a href="catalog.html">Catalog support</a></li>
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<li><a href="library.html">The parser interfaces</a></li>
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<li><a href="entities.html">Entities or no entities</a></li>
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<li><a href="namespaces.html">Namespaces</a></li>
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<li><a href="upgrade.html">Upgrading 1.x code</a></li>
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<li><a href="threads.html">Thread safety</a></li>
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<li><a href="DOM.html">DOM Principles</a></li>
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<li><a href="example.html">A real example</a></li>
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<li><a href="contribs.html">Contributions</a></li>
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<li>
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<a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a>
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</li>
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</ul></td></tr>
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</table>
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<table width="100%" border="0" cellspacing="1" cellpadding="3">
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<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
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<tr><td bgcolor="#fffacd"><ul style="margin-left: -2pt">
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<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
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<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
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<li><a href="http://www.cs.unibo.it/~casarini/gdome2/">DOM gdome2</a></li>
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<li><a href="ftp://xmlsoft.org/">FTP</a></li>
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<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
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<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
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<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Bug Tracker</a></li>
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</ul></td></tr>
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</table>
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</td></tr></table></td>
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<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">
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<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 contructs 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>
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<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>
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<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>
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<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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atributes with that URL. I suggest to use an URL within a domain you control,
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and that the URL should contain some kind of version information if possible.
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For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a good
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namespace scheme.</p>
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<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>
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<p>@@Interfaces@@</p>
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<p>@@Examples@@</p>
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<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>
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<p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>
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</td></tr></table></td></tr></table></td></tr></table></td>
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</tr></table></td></tr></table>
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</body>
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</html>
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