Gitiles
Code Review Sign In
gerrit-public.fairphone.software / fp2-dev / platform / external / libxml2 / 2d347fac9815f5c4a1c9073b4e04c892a5245c8a / . / doc / namespaces.html
blob: 79d01fb943238649bb3c387ef075af0325d29072 [file] [log] [blame]
Daniel Veillard43d3f612001-11-10 11:57:23 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]2<html>
3<head>
4<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">
5<style type="text/css"><!--
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame]6TD {font-family: Verdana,Arial,Helvetica}
7BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
8H1 {font-family: Verdana,Arial,Helvetica}
9H2 {font-family: Verdana,Arial,Helvetica}
10H3 {font-family: Verdana,Arial,Helvetica}
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]11A:link, A:visited, A:active { text-decoration: underline }
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]12--></style>
13<title>Namespaces</title>
14</head>
15<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
16<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
17<td width="180">
18<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>
19</td>
20<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">
21<h1>The XML C library for Gnome</h1>
22<h2>Namespaces</h2>
23</td></tr></table></td></tr></table></td>
24</tr></table>
25<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>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]26<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
27<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]28<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
Daniel Veillard8acca112002-01-21 09:52:27 +0000[diff] [blame]29<tr><td bgcolor="#fffacd"><ul>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]30<li><a href="index.html">Home</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]31<li><a href="intro.html">Introduction</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]32<li><a href="FAQ.html">FAQ</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]33<li><a href="docs.html">Documentation</a></li>
34<li><a href="bugs.html">Reporting bugs and getting help</a></li>
35<li><a href="help.html">How to help</a></li>
36<li><a href="downloads.html">Downloads</a></li>
37<li><a href="news.html">News</a></li>
Daniel Veillard7b602b42002-01-08 13:26:00 +0000[diff] [blame]38<li><a href="XMLinfo.html">XML</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]39<li><a href="XSLT.html">XSLT</a></li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]40<li><a href="python.html">Python and bindings</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]41<li><a href="architecture.html">libxml architecture</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]42<li><a href="tree.html">The tree output</a></li>
43<li><a href="interface.html">The SAX interface</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]44<li><a href="xmldtd.html">Validation &amp; DTDs</a></li>
45<li><a href="xmlmem.html">Memory Management</a></li>
46<li><a href="encoding.html">Encodings support</a></li>
47<li><a href="xmlio.html">I/O Interfaces</a></li>
48<li><a href="catalog.html">Catalog support</a></li>
49<li><a href="library.html">The parser interfaces</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]50<li><a href="entities.html">Entities or no entities</a></li>
51<li><a href="namespaces.html">Namespaces</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]52<li><a href="upgrade.html">Upgrading 1.x code</a></li>
Daniel Veillard52dcab32001-10-30 12:51:17 +0000[diff] [blame]53<li><a href="threads.html">Thread safety</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]54<li><a href="DOM.html">DOM Principles</a></li>
55<li><a href="example.html">A real example</a></li>
56<li><a href="contribs.html">Contributions</a></li>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]57<li>
58<a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a>
59</li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]60</ul></td></tr>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]61</table>
62<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard3bf65be2002-01-23 12:36:34 +0000[diff] [blame]63<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr>
64<tr><td bgcolor="#fffacd"><ul>
Daniel Veillardf8592562002-01-23 17:58:17 +0000[diff] [blame]65<li><a href="APIchunk0.html">Alphabetic</a></li>
Daniel Veillard3bf65be2002-01-23 12:36:34 +0000[diff] [blame]66<li><a href="APIconstructors.html">Constructors</a></li>
67<li><a href="APIfunctions.html">Functions/Types</a></li>
68<li><a href="APIfiles.html">Modules</a></li>
69<li><a href="APIsymbols.html">Symbols</a></li>
70</ul></td></tr>
71</table>
72<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]73<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
Daniel Veillard8acca112002-01-21 09:52:27 +0000[diff] [blame]74<tr><td bgcolor="#fffacd"><ul>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]75<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
76<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
Daniel Veillard4a859202002-01-08 11:49:22 +0000[diff] [blame]77<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
Daniel Veillard2d347fa2002-03-17 10:34:11 +0000[diff] [blame^]78<li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]79<li><a href="ftp://xmlsoft.org/">FTP</a></li>
80<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
Daniel Veillarddb9dfd92001-11-26 17:25:02 +0000[diff] [blame]81<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
Daniel Veillard2d347fa2002-03-17 10:34:11 +0000[diff] [blame^]82<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&amp;product=libxml2">Bug Tracker</a></li>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]83</ul></td></tr>
84</table>
85</td></tr></table></td>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]86<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">
87<p>The libxml library implements <a href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
88recognizing namespace contructs in the input, and does namespace lookup
89automatically when building the DOM tree. A namespace declaration is
90associated with an in-memory structure and all elements or attributes within
91that namespace point to it. Hence testing the namespace is a simple and fast
92equality operation at the user level.</p>
93<p>I suggest that people using libxml use a namespace, and declare it in the
94root element of their document as the default namespace. Then they don't need
95to use the prefix in the content but we will have a basis for future semantic
96refinement and merging of data from different sources. This doesn't increase
97the size of the XML output significantly, but significantly increases its
98value in the long-term. Example:</p>
99<pre>&lt;mydoc xmlns=&quot;http://mydoc.example.org/schemas/&quot;&gt;
100 &lt;elem1&gt;...&lt;/elem1&gt;
101 &lt;elem2&gt;...&lt;/elem2&gt;
102&lt;/mydoc&gt;</pre>
103<p>The namespace value has to be an absolute URL, but the URL doesn't have to
104point to any existing resource on the Web. It will bind all the element and
105atributes with that URL. I suggest to use an URL within a domain you control,
106and that the URL should contain some kind of version information if possible.
107For example, <code>&quot;http://www.gnome.org/gnumeric/1.0/&quot;</code> is a good
108namespace scheme.</p>
109<p>Then when you load a file, make sure that a namespace carrying the
110version-independent prefix is installed on the root element of your document,
111and if the version information don't match something you know, warn the user
112and be liberal in what you accept as the input. Also do *not* try to base
113namespace checking on the prefix value. &lt;foo:text&gt; may be exactly the
114same as &lt;bar:text&gt; in another document. What really matters is the URI
115associated with the element or the attribute, not the prefix string (which is
116just a shortcut for the full URI). In libxml, element and attributes have an
117<code>ns</code> field pointing to an xmlNs structure detailing the namespace
118prefix and its URI.</p>
119<p>@@Interfaces@@</p>
120<p>@@Examples@@</p>
121<p>Usually people object to using namespaces together with validity checking.
122I will try to make sure that using namespaces won't break validity checking,
123so even if you plan to use or currently are using validation I strongly
124suggest adding namespaces to your document. A default namespace scheme
125<code>xmlns=&quot;http://....&quot;</code> should not break validity even on less
126flexible parsers. Using namespaces to mix and differentiate content coming
127from multiple DTDs will certainly break current validation schemes. I will
128try to provide ways to do this, but this may not be portable or
129standardized.</p>
Daniel Veillard3f4c40f2002-02-13 09:19:28 +0000[diff] [blame]130<p><a href="bugs.html">Daniel Veillard</a></p>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]131</td></tr></table></td></tr></table></td></tr></table></td>
132</tr></table></td></tr></table>
133</body>
134</html>