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blob: 2e00b6e12a5b2b531306a9905e2d9f9151effdc2 [file] [log] [blame]
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]2 "http://www.w3.org/TR/REC-html40/loose.dtd">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]3<html>
4<head>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]5 <title>The XML library for Gnome</title>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]6 <meta name="GENERATOR" content="amaya V3.1">
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]8</head>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]9
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]10<body bgcolor="#ffffff">
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]11<p><a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome
12Logo"></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C
13Logo"></a></p>
14
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]15<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]16
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]17<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
18
19<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]20<ul>
21 <li><a href="#Introducti">Introduction</a></li>
22 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]23 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]24 <li><a href="#News">News</a></li>
25 <li><a href="#XML">XML</a></li>
26 <li><a href="#tree">The tree output</a></li>
27 <li><a href="#interface">The SAX interface</a></li>
28 <li><a href="#library">The XML library interfaces</a>
29 <ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]30 <li><a href="#Invoking">Invoking the parser: the pull way</a></li>
31 <li><a href="#Invoking">Invoking the parser: the push way</a></li>
32 <li><a href="#Invoking2">Invoking the parser: the SAX interface</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]33 <li><a href="#Building">Building a tree from scratch</a></li>
34 <li><a href="#Traversing">Traversing the tree</a></li>
35 <li><a href="#Modifying">Modifying the tree</a></li>
36 <li><a href="#Saving">Saving the tree</a></li>
37 <li><a href="#Compressio">Compression</a></li>
38 </ul>
39 </li>
40 <li><a href="#Entities">Entities or no entities</a></li>
41 <li><a href="#Namespaces">Namespaces</a></li>
42 <li><a href="#Validation">Validation</a></li>
43 <li><a href="#Principles">DOM principles</a></li>
44 <li><a href="#real">A real example</a></li>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]45 <li><a href="#Contributi">Contribution</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]46</ul>
47
48<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]49
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]50<p>This document describes libxml, the <a
51href="http://www.w3.org/XML/">XML</a> library provided in the <a
52href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
53building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]54
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]55<p>Here are some key points about libxml:</p>
56<ul>
57 <li>The internal document repesentation is as close as possible to the <a
58 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
59 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]60 like interface</a>; the interface is designed to be compatible with <a
61 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]62 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]63 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]64 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]65 HTML.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]66 <li>This library is released both under the <a
67 href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
68 IPR</a> and the GNU LGPL. Use either at your convenience, basically this
69 should make everybody happy, if not, drop me a mail.</li>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]70 <li>There is <a href="upgrade.html">a first set of instructions</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]71 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]72</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]73
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]74<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]75
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]76<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]77<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]78 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]79 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
80 automatically extracted.</li>
81 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]82 examples</a> on how to use libxml.</li>
83 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
84 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
85 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]86 <li>George Lebl wrote <a
87 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]88 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]89 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
90 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
91 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]92 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]93 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
94 href="http://www.levien.com/svg/">gill</a>. Check his <a
95 href="http://www.levien.com/gnome/domination.html">DOMination
96 paper</a>.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]97 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO
98 file</a></li>
99 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are
100 starting a new project using libxml you should really use the 2.x
101 version.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]102 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]103 archive</a>.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]104</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]105
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]106<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]107
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]108<p>Well, bugs or missing features are always possible, and I will make a point
109of fixing them in a timely fashion. The best way to report a bug is to <a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]110href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]111database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]112reminder when a bug is still open. Check the <a
113href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]114and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]115
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]116<p>There is also a mailing-list <a
117href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
118href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]119majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]120href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
121"subscribe xml" in the <strong>content</strong> of the message.</p>
122
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]123<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]124href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]125
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]126<p>Of course, bugs reports with a suggested patch for fixing them will
127probably be processed faster.</p>
128
129<p>If you're looking for help, a quick look at <a
130href="http://xmlsoft.org/messages/#407">the list archive</a> may actually
131provide the answer, I usually send source samples when answering libxml usage
132questions. The <a href="http://xmlsoft.org/book1.html">auto-generated
133documentantion</a> is not as polished as I would like (i need to learn more
134about Docbook), but it's a good starting point.</p>
135
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]136<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]137
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]138<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]139href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]140href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]141as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]142archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPM
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]143packages</a>. (NOTE that you need both the <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]144href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
145href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]146packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]147
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]148<p><a name="Snapshot">Snapshot:</a></p>
149<ul>
150 <li>Code from the W3C cvs base libxml <a
151 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
152 <li>Docs, content of the web site, the list archive included <a
153 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
154</ul>
155
156<p><a name="Contribs">Contribs:</a></p>
157
158<p>I do accept external contributions, especially if compiling on another
159platform, get in touch with me to upload the package. I will keep them in the
160<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
161
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]162<p>Libxml is also available from 2 CVS bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]163<ul>
164 <li><p>The <a href="http://dev.w3.org/cvsweb/XML/">W3C CVS base</a>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]165 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]166 this base for my own development, so it's updated more regularly, but the
167 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]168 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]169 password: anonymous
170 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]171 </li>
172 <li><p>The <a
173 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&amp;dir=gnome-xml">Gnome
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]174 CVS base</a>. Check the <a
175 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
176 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]177 </li>
178</ul>
179
180<h2><a name="News">News</a></h2>
181
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]182<h3>CVS only : check the <a
183href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
184for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]185<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]186 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]187 if you want to test those.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]188</ul>
189
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]190<h3>2.0.0: Apr 12 2000</h3>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]191<ul>
192 <li>First public release of libxml2. If you are using libxml, it's a good
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]193 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initally
194 scheduled for Apr 3 the relase occured only on Apr 12 due to massive
195 workload.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]196 <li>The include are now located under $prefix/include/libxml (instead of
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]197 $prefix/include/gnome-xml), they also are referenced by
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]198 <pre>#include &lt;libxml/xxx.h></pre>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]199 <p>instead of</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]200 <pre>#include "xxx.h"</pre>
201 </li>
Daniel Veillard8f621982000-03-20 13:07:15 +0000[diff] [blame]202 <li>a new URI module for parsing URIs and following strictly RFC 2396</li>
203 <li>the memory allocation routines used by libxml can now be overloaded
204 dynamically by using xmlMemSetup()</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]205 <li>The previously CVS only tool tester has been renamed
206 <strong>xmllint</strong> and is now installed as part of the libxml2
207 package</li>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]208 <li>The I/O interface has been revamped. There is now ways to plug in
209 specific I/O modules, either at the URI scheme detection level using
210 xmlRegisterInputCallbacks() or by passing I/O functions when creating a
211 parser context using xmlCreateIOParserCtxt()</li>
212 <li>there is a C preprocessor macro LIBXML_VERSION providing the version
213 number of the libxml module in use</li>
214 <li>a number of optional features of libxml can now be excluded at configure
215 time (FTP/HTTP/HTML/XPath/Debug)</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]216</ul>
217
218<h3>2.0.0beta: Mar 14 2000</h3>
219<ul>
220 <li>This is a first Beta release of libxml version 2</li>
221 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
222 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
223 tar and RPMs</li>
224 <li>This version is now the head in the Gnome CVS base, the old one is
225 available under the tag LIB_XML_1_X</li>
226 <li>This includes a very large set of changes. Froma programmatic point of
227 view applications should not have to be modified too much, check the <a
228 href="upgrade.html">upgrade page</a></li>
229 <li>Some interfaces may changes (especially a bit about encoding).</li>
230 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]231 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]232 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
233 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]234 <li>Better handling of entities, especially well formedness checking and
235 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]236 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]237 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]238 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
239 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]240 </ul>
241 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]242 <li>Serious progress were made toward compliance, <a
243 href="conf/result.html">here are the result of the test</a> against the
244 OASIS testsuite (except the japanese tests since I don't support that
245 encoding yet). This URL is rebuilt every couple of hours using the CVS
246 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]247</ul>
248
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]249<h3>1.8.7: Mar 6 2000</h3>
250<ul>
251 <li>This is a bug fix release:</li>
252 <li>It is possible to disable the ignorable blanks heuristic used by
253 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
254 that for adherence to XML spec, this behaviour will be disabled by default
255 in 2.x . The same function will allow to keep compatibility for old
256 code.</li>
257 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
258 heuristic is really the Right Way :-\</li>
259 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
260 compilation on some platforms has been fixed</li>
261 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
262 URIs</li>
263</ul>
264
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]265<h3>1.8.6: Jan 31 2000</h3>
266<ul>
267 <li>added a nanoFTP transport module, debugged until the new version of <a
268 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
269 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]270</ul>
271
272<h3>1.8.5: Jan 21 2000</h3>
273<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]274 <li>adding APIs to parse a well balanced chunk of XML (production <a
275 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
276 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]277 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
278 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
279 solve the zlib checks problems</li>
280 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
281 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]282</ul>
283
284<h3>1.8.4: Jan 13 2000</h3>
285<ul>
286 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
287 <li>all exit() call should have been removed from libxml</li>
288 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
289 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]290</ul>
291
292<h3>1.8.3: Jan 5 2000</h3>
293<ul>
294 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]295 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]296 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]297 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]298 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
299 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]300 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]301 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]302 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]303</ul>
304
305<h3>1.8.2: Dec 21 1999</h3>
306<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]307 <li>I got another problem with includes and C++, I hope this issue is fixed
308 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]309 <li>Added a few tree modification functions: xmlReplaceNode,
310 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
311 xmlDocSetRootElement</li>
312 <li>Tried to improve the HTML output with help from <a
313 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]314</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]315
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]316<h3>1.8.1: Dec 18 1999</h3>
317<ul>
318 <li>various patches to avoid troubles when using libxml with C++ compilers
319 the "namespace" keyword and C escaping in include files</li>
320 <li>a problem in one of the core macros IS_CHAR was corrected</li>
321 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
322 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]323 <li>fixed a posteriori validation (validation after parsing, or by using a
324 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]325 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]326</ul>
327
328<h3>1.8.0: Dec 12 1999</h3>
329<ul>
330 <li>cleanup, especially memory wise</li>
331 <li>the parser should be more reliable, especially the HTML one, it should
332 not crash, whatever the input !</li>
333 <li>Integrated various patches, especially a speedup improvement for large
334 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
335 configure with --with-buffers to enable them.</li>
336 <li>attribute normalization, oops should have been added long ago !</li>
337 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
338 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]339</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]340
341<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]342<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]343 <li>Lots of HTML improvement</li>
344 <li>Fixed some errors when saving both XML and HTML</li>
345 <li>More examples, the regression tests should now look clean</li>
346 <li>Fixed a bug with contiguous charref</li>
347</ul>
348
349<h3>1.7.3: Sep 29 1999</h3>
350<ul>
351 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]352 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]353 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]354</ul>
355
356<h3>1.7.1: Sep 24 1999</h3>
357<ul>
358 <li>The basic type for strings manipulated by libxml has been renamed in
359 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
360 is that CHAR was conflicting with a predefined type on Windows. However on
361 non WIN32 environment, compatibility is provided by the way of a
362 <strong>#define </strong>.</li>
363 <li>Changed another error : the use of a structure field called errno, and
364 leading to troubles on platforms where it's a macro</li>
365</ul>
366
367<h3>1.7.0: sep 23 1999</h3>
368<ul>
369 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
370 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
371 <li>Added an errno to report errors by another mean than a simple printf
372 like callback</li>
373 <li>Finished ID/IDREF support and checking when validation</li>
374 <li>Serious memory leaks fixed (there is now a <a
375 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
376 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
377 implementation</li>
378 <li>Added an HTML parser front-end</li>
379</ul>
380
381<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]382
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]383<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]384markup-based structured documents. Here is <a name="example">an example XML
385document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]386<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]387&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]388 &lt;head>
389 &lt;title>Welcome to Gnome&lt;/title>
390 &lt;/head>
391 &lt;chapter>
392 &lt;title>The Linux adventure&lt;/title>
393 &lt;p>bla bla bla ...&lt;/p>
394 &lt;image href="linus.gif"/>
395 &lt;p>...&lt;/p>
396 &lt;/chapter>
397&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]398
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]399<p>The first line specifies that it's an XML document and gives useful
400information about its encoding. Then the document is a text format whose
401structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]402to be closed</strong>. XML is pedantic about this. However, if a tag is empty
403(no content), a single tag can serve as both the opening and closing tag if it
404ends with <code>/></code> rather than with <code>></code>. Note that, for
405example, the image tag has no content (just an attribute) and is closed by
406ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]407
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]408<p>XML can be applied sucessfully to a wide range of uses, from long term
409structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]410data encoding mechanisms like configuration file formatting (glade),
411spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
412it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]413
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]414<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]415
416<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]417returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]418<strong>xmlDoc</strong> structure). This structure contains information such
419as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]420is the root of the document (or more exactly the first child under the root
421which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]422in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]423An xmlNode can also carry properties (a chain of xmlAttr structures). An
424attribute may have a value which is a list of TEXT or ENTITY_REF nodes.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]425
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]426<p>Here is an example (erroneous with respect to the XML spec since there
427should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]428
429<p><img src="structure.gif" alt=" structure.gif "></p>
430
431<p>In the source package there is a small program (not installed by default)
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]432called <strong>xmllint</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]433prints them back as parsed. This is useful for detecting errors both in XML
434code and in the XML parser itself. It has an option <strong>--debug</strong>
435which prints the actual in-memory structure of the document, here is the
436result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]437<pre>DOCUMENT
438version=1.0
439standalone=true
440 ELEMENT EXAMPLE
441 ATTRIBUTE prop1
442 TEXT
443 content=gnome is great
444 ATTRIBUTE prop2
445 ENTITY_REF
446 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]447 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]448 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]449 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]450 TEXT
451 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]452 ELEMENT chapter
453 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]454 TEXT
455 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]456 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]457 TEXT
458 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]459 ELEMENT image
460 ATTRIBUTE href
461 TEXT
462 content=linus.gif
463 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]464 TEXT
465 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]466
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]467<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]468
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]469<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]470
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]471<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]472memory. In that case (and if you don't expect to save back the XML document
473loaded using libxml), it's better to use the SAX interface of libxml. SAX is a
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]474<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]475application layer registers a customized set of callbacks which are called by
476the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]477
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]478<p>To get more detailed step-by-step guidance on using the SAX interface of
479libxml, see the
480href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]481documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]482Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]483
484<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
485program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]486binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]487distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]488testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]489<pre>SAX.setDocumentLocator()
490SAX.startDocument()
491SAX.getEntity(amp)
492SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
493SAX.characters( , 3)
494SAX.startElement(head)
495SAX.characters( , 4)
496SAX.startElement(title)
497SAX.characters(Welcome to Gnome, 16)
498SAX.endElement(title)
499SAX.characters( , 3)
500SAX.endElement(head)
501SAX.characters( , 3)
502SAX.startElement(chapter)
503SAX.characters( , 4)
504SAX.startElement(title)
505SAX.characters(The Linux adventure, 19)
506SAX.endElement(title)
507SAX.characters( , 4)
508SAX.startElement(p)
509SAX.characters(bla bla bla ..., 15)
510SAX.endElement(p)
511SAX.characters( , 4)
512SAX.startElement(image, href='linus.gif')
513SAX.endElement(image)
514SAX.characters( , 4)
515SAX.startElement(p)
516SAX.characters(..., 3)
517SAX.endElement(p)
518SAX.characters( , 3)
519SAX.endElement(chapter)
520SAX.characters( , 1)
521SAX.endElement(EXAMPLE)
522SAX.endDocument()</pre>
523
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]524<p>Most of the other functionalities of libxml are based on the DOM
525tree-building facility, so nearly everything up to the end of this document
526presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]527itself is built by a set of registered default callbacks, without internal
528specific interface.</p>
529
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]530<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]531
532<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]533using the XML library from the C language. It is not intended to be extensive.
534I hope the automatically generated documents will provide the completeness
535required, but as a separate set of documents. The interfaces of the XML
536library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]537interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]538
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]539<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]540separated from the <a href="gnome-xml-htmlparser.html">HTML parser
541interfaces</a>. Let's have a look at how the XML parser can be called:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]542
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]543<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]544
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]545<p>Usually, the first thing to do is to read an XML input. The parser accepts
546documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]547defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]548<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]549 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]550 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]551 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]552</dl>
553<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]554 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]555 <dd><p>Parse an XML document contained in a (possibly compressed)
556 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]557 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]558</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]559
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]560<p>The parser returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]561failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]562
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]563<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]564
565<p>In order for the application to keep the control when the document is been
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]566fetched (which is common for GUI based programs) libxml provides a push
567interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]568<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
569 void *user_data,
570 const char *chunk,
571 int size,
572 const char *filename);
573int xmlParseChunk (xmlParserCtxtPtr ctxt,
574 const char *chunk,
575 int size,
576 int terminate);</pre>
577
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]578<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]579<pre> FILE *f;
580
581 f = fopen(filename, "r");
582 if (f != NULL) {
583 int res, size = 1024;
584 char chars[1024];
585 xmlParserCtxtPtr ctxt;
586
587 res = fread(chars, 1, 4, f);
588 if (res > 0) {
589 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
590 chars, res, filename);
591 while ((res = fread(chars, 1, size, f)) > 0) {
592 xmlParseChunk(ctxt, chars, res, 0);
593 }
594 xmlParseChunk(ctxt, chars, 0, 1);
595 doc = ctxt->myDoc;
596 xmlFreeParserCtxt(ctxt);
597 }
598 }</pre>
599
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]600<p>Also note that the HTML parser embedded into libxml also has a push
601interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]602
603<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
604
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]605<p>A couple of comments can be made, first this mean that the parser is
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]606memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]607Reading a document without building the tree is possible using the SAX
608interfaces (see SAX.h and <a
609href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]610Henstridge's documentation</a>). Note also that the push interface can be
611limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]612<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]613
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]614<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]615
616<p>The other way to get an XML tree in memory is by building it. Basically
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]617there is a set of functions dedicated to building new elements. (These are
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]618also described in &lt;libxml/tree.h>.) For example, here is a piece of code
619that produces the XML document used in the previous examples:</p>
620<pre> #include &lt;libxml/tree.h>
621 xmlDocPtr doc;
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]622 xmlNodePtr tree, subtree;
623
624 doc = xmlNewDoc("1.0");
625 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
626 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]627 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]628 tree = xmlNewChild(doc->root, NULL, "head", NULL);
629 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
630 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
631 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
632 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
633 subtree = xmlNewChild(tree, NULL, "image", NULL);
634 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]635
636<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]637
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]638<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]639
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]640<p>Basically by <a href="gnome-xml-tree.html">including "tree.h"</a> your code
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]641has access to the internal structure of all the elements of the tree. The
642names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]643<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]644<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]645example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]646<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]647
648<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]649<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]650
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]651<p>points to the text node containing the chapter title "The Linux
652adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]653
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]654<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]655present before the document root, so <code>doc->root</code> may point to an
656element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]657<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]658
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]659<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]660
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]661<p>Functions are provided for reading and writing the document content. Here
662is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]663<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]664 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
665 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]666 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
667 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]668 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]669</dl>
670<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]671 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]672 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]673 <dd><p>This function returns a pointer to the property content. Note that
674 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]675 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]676</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]677
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]678<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]679elements:</p>
680<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]681 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]682 *value);</code></dt>
683 <dd><p>This function takes an "external" string and convert it to one text
684 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]685 entity references like &amp;Gnome; will be stored internally as entity
686 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]687 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]688</dl>
689<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]690 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]691 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]692 <dd><p>This function is the inverse of
693 <code>xmlStringGetNodeList()</code>. It generates a new string
694 containing the content of the text and entity nodes. Note the extra
695 argument inLine. If this argument is set to 1, the function will expand
696 entity references. For example, instead of returning the &amp;Gnome;
697 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]698 "GNU Network Object Model Environment"). Set this argument if you want
699 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]700 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]701</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]702
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]703<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]704
705<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]706<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]707 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]708 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]709 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]710 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]711</dl>
712<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]713 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]714 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]715 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]716</dl>
717<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]718 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]719 <dd><p>Saves the document to a file. In this case, the compression
720 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]721 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]722</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]723
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]724<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]725
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]726<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]727accesses. The level of compression on saves can be turned on either globally
728or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]729<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]730 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]731 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]732 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]733</dl>
734<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]735 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]736 <dd><p>Sets the document compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]737 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]738</dl>
739<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]740 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]741 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]742 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]743</dl>
744<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]745 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]746 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]747 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]748</dl>
749
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]750<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]751
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]752<p>Entities in principle are similar to simple C macros. An entity defines an
753abbreviation for a given string that you can reuse many times throughout the
754content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]755may occur frequently within a document, or to confine the change needed to a
756document to a restricted area in the internal subset of the document (at the
757beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]758<pre>1 &lt;?xml version="1.0"?>
7592 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
7603 &lt;!ENTITY xml "Extensible Markup Language">
7614 ]>
7625 &lt;EXAMPLE>
7636 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7647 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]765
766<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]767it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]768are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]769predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]770<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
771for the character '>', <strong>&amp;apos;</strong> for the character ''',
772<strong>&amp;quot;</strong> for the character '"', and
773<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]774
775<p>One of the problems related to entities is that you may want the parser to
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]776substitute an entity's content so that you can see the replacement text in
777your application. Or you may prefer to keep entity references as such in the
778content to be able to save the document back without losing this usually
779precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]780entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]781them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]782href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]783function allows you to check and change the behaviour, which is to not
784substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]785
786<p>Here is the DOM tree built by libxml for the previous document in the
787default case:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]788<pre>/gnome/src/gnome-xml -> ./xmllint --debug test/ent1
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]789DOCUMENT
790version=1.0
791 ELEMENT EXAMPLE
792 TEXT
793 content=
794 ENTITY_REF
795 INTERNAL_GENERAL_ENTITY xml
796 content=Extensible Markup Language
797 TEXT
798 content=</pre>
799
800<p>And here is the result when substituting entities:</p>
801<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
802DOCUMENT
803version=1.0
804 ELEMENT EXAMPLE
805 TEXT
806 content= Extensible Markup Language</pre>
807
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]808<p>So, entities or no entities? Basically, it depends on your use case. I
809suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]810entities in your XML document or data if you are not willing to handle the
811entity references elements in the DOM tree.</p>
812
813<p>Note that at save time libxml enforce the conversion of the predefined
814entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]815transparently replace those with chars (i.e., it will not generate entity
816reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]817finding them in the input).</p>
818
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]819<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]820
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]821<p>The libxml library implements <a
822href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
823recognizing namespace contructs in the input, and does namespace lookup
824automatically when building the DOM tree. A namespace declaration is
825associated with an in-memory structure and all elements or attributes within
826that namespace point to it. Hence testing the namespace is a simple and fast
827equality operation at the user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]828
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]829<p>I suggest that people using libxml use a namespace, and declare it in the
830root element of their document as the default namespace. Then they don't need
831to use the prefix in the content but we will have a basis for future semantic
832refinement and merging of data from different sources. This doesn't augment
833significantly the size of the XML output, but significantly increase its value
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]834in the long-term. Example:</p>
835<pre>&lt;mydoc xmlns="http://mydoc.example.org/schemas/">
836 &lt;elem1>...&lt;/elem1>
837 &lt;elem2>...&lt;/elem2>
838&lt;/mydoc></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]839
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]840<p>Concerning the namespace value, this has to be an URL, but the URL doesn't
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]841have to point to any existing resource on the Web. It will bind all the
842element and atributes with that URL. I suggest to use an URL within a domain
843you control, and that the URL should contain some kind of version information
844if possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]845a good namespace scheme.</p>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]846
847<p>Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]848version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]849and if the version information don't match something you know, warn the user
850and be liberal in what you accept as the input. Also do *not* try to base
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]851namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]852as &lt;bar:text> in another document. What really matter is the URI associated
853with the element or the attribute, not the prefix string (which is just a
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]854shortcut for the full URI). In libxml element and attributes have a
855<code>ns</code> field pointing to an xmlNs structure detailing the namespace
856prefix and it's URI.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]857
858<p>@@Interfaces@@</p>
859
860<p>@@Examples@@</p>
861
862<p>Usually people object using namespace in the case of validation, I object
863this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]864so even is you plan to use or currently are using validation I strongly
865suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]866<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]867flexible parsers. Now using namespace to mix and differentiate content coming
868from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]869to provide ways to do this, but this may not be portable or standardized.</p>
870
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]871<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]872
873<p>Well what is validation and what is a DTD ?</p>
874
875<p>Validation is the process of checking a document against a set of
876construction rules, a <strong>DTD</strong> (Document Type Definition) is such
877a set of rules.</p>
878
879<p>The validation process and building DTDs are the two most difficult parts
880of XML life cycle. Briefly a DTD defines all the possibles element to be
881found within your document, what is the formal shape of your document tree (by
882defining the allowed content of an element, either text, a regular expression
883for the allowed list of children, or mixed content i.e. both text and childs).
884The DTD also defines the allowed attributes for all elements and the types of
885the attributes. For more detailed informations, I suggest to read the related
886parts of the XML specification, the examples found under
887gnome-xml/test/valid/dtd and the large amount of books available on XML. The
888dia example in gnome-xml/test/valid should be both simple and complete enough
889to allow you to build your own.</p>
890
891<p>A word of warning, building a good DTD which will fit your needs of your
892application in the long-term is far from trivial, however the extra level of
893quality it can insure is well worth the price for some sets of applications or
894if you already have already a DTD defined for your application field.</p>
895
896<p>The validation is not completely finished but in a (very IMHO) usable
897state. Until a real validation interface is defined the way to do it is to
898define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
899variable to 1, this will of course be changed at some point:</p>
900
901<p>extern int xmlDoValidityCheckingDefaultValue;</p>
902
903<p>...</p>
904
905<p>xmlDoValidityCheckingDefaultValue = 1;</p>
906
907<p></p>
908
909<p>To handle external entities, use the function
910<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
911link in you HTTP/FTP/Entities database library to the standard libxml
912core.</p>
913
914<p>@@interfaces@@</p>
915
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]916<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]917
918<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document Object
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]919Model</em> this is an API for accessing XML or HTML structured documents.
920Native support for DOM in Gnome is on the way (module gnome-dom), and it will
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]921be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]922files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]923set of IDL (or Java) interfaces allowing to traverse and manipulate a
924document. The DOM library will allow accessing and modifying "live" documents
925presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]926
927<p><img src="DOM.gif" alt=" DOM.gif "></p>
928
929<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]930embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]931
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]932<p>The current DOM implementation on top of libxml is the <a
933href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
934a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
935Levien</a>.</p>
936
937<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
938
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]939<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]940
941<p>Here is a real size example, where the actual content of the application
942data is not kept in the DOM tree but uses internal structures. It is based on
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]943a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]944storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
945base</a>:</p>
946<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]947&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
948 &lt;gjob:Jobs>
949
950 &lt;gjob:Job>
951 &lt;gjob:Project ID="3"/>
952 &lt;gjob:Application>GBackup&lt;/gjob:Application>
953 &lt;gjob:Category>Development&lt;/gjob:Category>
954
955 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]956 &lt;gjob:Status>Open&lt;/gjob:Status>
957 &lt;gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST&lt;/gjob:Modified>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]958 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
959 &lt;/gjob:Update>
960
961 &lt;gjob:Developers>
962 &lt;gjob:Developer>
963 &lt;/gjob:Developer>
964 &lt;/gjob:Developers>
965
966 &lt;gjob:Contact>
967 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]968 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]969 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]970 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]971 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]972 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]973 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]974 &lt;/gjob:Webpage>
975 &lt;gjob:Snailmail>
976 &lt;/gjob:Snailmail>
977 &lt;gjob:Phone>
978 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]979 &lt;/gjob:Contact>
980
981 &lt;gjob:Requirements>
982 The program should be released as free software, under the GPL.
983 &lt;/gjob:Requirements>
984
985 &lt;gjob:Skills>
986 &lt;/gjob:Skills>
987
988 &lt;gjob:Details>
989 A GNOME based system that will allow a superuser to configure
990 compressed and uncompressed files and/or file systems to be backed
991 up with a supported media in the system. This should be able to
992 perform via find commands generating a list of files that are passed
993 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
994 or via operations performed on the filesystem itself. Email
995 notification and GUI status display very important.
996 &lt;/gjob:Details>
997
998 &lt;/gjob:Job>
999
1000 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1001&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1002
1003<p>While loading the XML file into an internal DOM tree is a matter of calling
1004only a couple of functions, browsing the tree to gather the informations and
1005generate the internals structures is harder, and more error prone.</p>
1006
1007<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]1008structure. For example, the ordering of the attributes is not significant,
1009Cthe XML specification is clear about it. It's also usually a good idea to not
1010be dependent of the orders of the childs of a given node, unless it really
1011makes things harder. Here is some code to parse the informations for a
1012person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1013<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1014 * A person record
1015 */
1016typedef struct person {
1017 char *name;
1018 char *email;
1019 char *company;
1020 char *organisation;
1021 char *smail;
1022 char *webPage;
1023 char *phone;
1024} person, *personPtr;
1025
1026/*
1027 * And the code needed to parse it
1028 */
1029personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1030 personPtr ret = NULL;
1031
1032DEBUG("parsePerson\n");
1033 /*
1034 * allocate the struct
1035 */
1036 ret = (personPtr) malloc(sizeof(person));
1037 if (ret == NULL) {
1038 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1039 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1040 }
1041 memset(ret, 0, sizeof(person));
1042
1043 /* We don't care what the top level element name is */
1044 cur = cur->childs;
1045 while (cur != NULL) {
1046 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1047 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1048 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1049 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
1050 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1051 }
1052
1053 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1054}</pre>
1055
1056<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1057<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1058 <li>Usually a recursive parsing style is the more convenient one, XML data
1059 being by nature subject to repetitive constructs and usualy exibit highly
1060 stuctured patterns.</li>
1061 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1062 the pointer to the global XML document and the namespace reserved to the
1063 application. Document wide information are needed for example to decode
1064 entities and it's a good coding practice to define a namespace for your
1065 application set of data and test that the element and attributes you're
1066 analyzing actually pertains to your application space. This is done by a
1067 simple equality test (cur->ns == ns).</li>
1068 <li>To retrieve text and attributes value, it is suggested to use the
1069 function <em>xmlNodeListGetString</em> to gather all the text and entity
1070 reference nodes generated by the DOM output and produce an single text
1071 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1072</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1073
1074<p>Here is another piece of code used to parse another level of the
1075structure:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]1076<pre>#include &lt;libxml/tree.h>
1077/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1078 * a Description for a Job
1079 */
1080typedef struct job {
1081 char *projectID;
1082 char *application;
1083 char *category;
1084 personPtr contact;
1085 int nbDevelopers;
1086 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1087} job, *jobPtr;
1088
1089/*
1090 * And the code needed to parse it
1091 */
1092jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1093 jobPtr ret = NULL;
1094
1095DEBUG("parseJob\n");
1096 /*
1097 * allocate the struct
1098 */
1099 ret = (jobPtr) malloc(sizeof(job));
1100 if (ret == NULL) {
1101 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1102 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1103 }
1104 memset(ret, 0, sizeof(job));
1105
1106 /* We don't care what the top level element name is */
1107 cur = cur->childs;
1108 while (cur != NULL) {
1109
1110 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1111 ret->projectID = xmlGetProp(cur, "ID");
1112 if (ret->projectID == NULL) {
1113 fprintf(stderr, "Project has no ID\n");
1114 }
1115 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1116 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1117 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1118 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1119 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1120 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1121 ret->contact = parsePerson(doc, ns, cur);
1122 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1123 }
1124
1125 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1126}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1127
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1128<p>One can notice that once used to it, writing this kind of code is quite
1129simple, but boring. Ultimately, it could be possble to write stubbers taking
1130either C data structure definitions, a set of XML examples or an XML DTD and
1131produce the code needed to import and export the content between C data and
1132XML storage. This is left as an exercise to the reader :-)</p>
1133
1134<p>Feel free to use <a href="gjobread.c">the code for the full C parsing
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1135example</a> as a template, it is also available with Makefile in the Gnome CVS
1136base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1137
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]1138<h2><a name="Contributi">Contributions</a></h2>
1139<ul>
1140 <li><a href="mailto:ari@btigate.com">Ari Johnson</a> provides a C++ wrapper
1141 for libxml:
1142 <p>Website: <a
1143 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p>
1144 <p>Download: <a
1145 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p>
1146 </li>
1147 <li><a href="mailto:doolin@cs.utk.edu">David Doolin</a> provides a
1148 precompiled Windows version
1149 <p><a
1150 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p>
1151 </li>
1152 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> provided a emacs
1153 module to lookup libxml functions documentation</li>
1154 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a
1155 href="http://xmlsoft.org/messages/0488.html">man pages</a> (not yet
1156 integrated in the distribution)</li>
1157</ul>
1158
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1159<p></p>
1160
1161<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1162
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame^]1163<p>$Id: xml.html,v 1.33 2000/04/16 08:52:20 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1164</body>
1165</html>