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gerrit-public.fairphone.software / platform / external / libxml2 / d30be4add765e2c16840c4f2aab25f447384c7b2 / . / doc / catalog.html
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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">
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3<head>
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13<title>Catalog support</title>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]14</head>
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16<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
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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>
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21<h1>The XML C library for Gnome</h1>
22<h2>Catalog support</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>
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27<table width="100%" border="0" cellspacing="1" cellpadding="3">
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 Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]30<li><a href="index.html">Home</a></li>
31<li><a href="intro.html">Introduction</a></li>
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Daniel Veillard7b602b42002-01-08 13:26:00 +0000[diff] [blame]38<li><a href="XMLinfo.html">XML</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +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>
42<li><a href="tree.html">The tree output</a></li>
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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>
50<li><a href="entities.html">Entities or no entities</a></li>
51<li><a href="namespaces.html">Namespaces</a></li>
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 Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]54<li><a href="DOM.html">DOM Principles</a></li>
55<li><a href="example.html">A real example</a></li>
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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>
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Daniel Veillardb8cfbd12001-10-25 10:53:28 +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 Veillardb8cfbd12001-10-25 10:53:28 +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 Veillardb8cfbd12001-10-25 10:53:28 +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 Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]83</ul></td></tr>
84</table>
85</td></tr></table></td>
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">
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]87<p>Table of Content:</p>
88<ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]89<li><a href="General2">General overview</a></li>
90<li><a href="#definition">The definition</a></li>
91<li><a href="#Simple">Using catalogs</a></li>
92<li><a href="#Some">Some examples</a></li>
93<li><a href="#reference">How to tune catalog usage</a></li>
94<li><a href="#validate">How to debug catalog processing</a></li>
95<li><a href="#Declaring">How to create and maintain catalogs</a></li>
96<li><a href="#implemento">The implementor corner quick review of the
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]97 API</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]98<li><a href="#Other">Other resources</a></li>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]99</ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]100<h3><a name="General2">General overview</a></h3>
101<p>What is a catalog? Basically it's a lookup mechanism used when an entity
102(a file or a remote resource) references another entity. The catalog lookup
103is inserted between the moment the reference is recognized by the software
104(XML parser, stylesheet processing, or even images referenced for inclusion
105in a rendering) and the time where loading that resource is actually
106started.</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]107<p>It is basically used for 3 things:</p>
108<ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]109<li>mapping from &quot;logical&quot; names, the public identifiers and a more
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]110 concrete name usable for download (and URI). For example it can associate
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]111 the logical name
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]112 <p>&quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;</p>
113<p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]114 downloaded</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]115<p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p>
116</li>
117<li>remapping from a given URL to another one, like an HTTP indirection
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]118 saying that
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]119 <p>&quot;http://www.oasis-open.org/committes/tr.xsl&quot;</p>
120<p>should really be looked at</p>
121<p>&quot;http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl&quot;</p>
122</li>
123<li>providing a local cache mechanism allowing to load the entities
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]124 associated to public identifiers or remote resources, this is a really
125 important feature for any significant deployment of XML or SGML since it
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]126 allows to avoid the aleas and delays associated to fetching remote
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]127 resources.</li>
128</ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]129<h3><a name="definition">The definitions</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]130<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p>
131<ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]132<li>the older SGML catalogs, the official spec is SGML Open Technical
133 Resolution TR9401:1997, but is better understood by reading <a href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]134 James Clark. This is relatively old and not the preferred mode of
135 operation of libxml.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]136<li>
137<a href="http://www.oasis-open.org/committees/entity/spec.html">XML
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]138 Catalogs</a> is far more flexible, more recent, uses an XML syntax and
139 should scale quite better. This is the default option of libxml.</li>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]140</ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]141<p>
142<h3><a name="Simple">Using catalog</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]143<p>In a normal environment libxml will by default check the presence of a
144catalog in /etc/xml/catalog, and assuming it has been correctly populated,
145the processing is completely transparent to the document user. To take a
146concrete example, suppose you are authoring a DocBook document, this one
147starts with the following DOCTYPE definition:</p>
148<pre>&lt;?xml version='1.0'?&gt;
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]149&lt;!DOCTYPE book PUBLIC &quot;-//Norman Walsh//DTD DocBk XML V3.1.4//EN&quot;
150 &quot;http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd&quot;&gt;</pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]151<p>When validating the document with libxml, the catalog will be
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]152automatically consulted to lookup the public identifier &quot;-//Norman Walsh//DTD
153DocBk XML V3.1.4//EN&quot; and the system identifier
154&quot;http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd&quot;, and if these entities have
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]155been installed on your system and the catalogs actually point to them, libxml
156will fetch them from the local disk.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]157<p style="font-size: 10pt">
158<strong>Note</strong>: Really don't use this
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]159DOCTYPE example it's a really old version, but is fine as an example.</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]160<p>Libxml will check the catalog each time that it is requested to load an
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]161entity, this includes DTD, external parsed entities, stylesheets, etc ... If
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]162your system is correctly configured all the authoring phase and processing
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]163should use only local files, even if your document stays portable because it
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]164uses the canonical public and system ID, referencing the remote document.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]165<h3><a name="Some">Some examples:</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]166<p>Here is a couple of fragments from XML Catalogs used in libxml early
167regression tests in <code>test/catalogs</code> :</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]168<pre>&lt;?xml version=&quot;1.0&quot;?&gt;
169&lt;!DOCTYPE catalog PUBLIC
170 &quot;-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN&quot;
171 &quot;http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd&quot;&gt;
172&lt;catalog xmlns=&quot;urn:oasis:names:tc:entity:xmlns:xml:catalog&quot;&gt;
173 &lt;public publicId=&quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
174 uri=&quot;http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]175...</pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]176<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are
177written in XML, there is a specific namespace for catalog elements
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]178&quot;urn:oasis:names:tc:entity:xmlns:xml:catalog&quot;. The first entry in this
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]179catalog is a <code>public</code> mapping it allows to associate a Public
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]180Identifier with an URI.</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]181<pre>...
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]182 &lt;rewriteSystem systemIdStartString=&quot;http://www.oasis-open.org/docbook/&quot;
183 rewritePrefix=&quot;file:///usr/share/xml/docbook/&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]184...</pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]185<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that
186any URI starting with a given prefix should be looked at another URI
187constructed by replacing the prefix with an new one. In effect this acts like
188a cache system for a full area of the Web. In practice it is extremely useful
189with a file prefix if you have installed a copy of those resources on your
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]190local system.</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]191<pre>...
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]192&lt;delegatePublic publicIdStartString=&quot;-//OASIS//DTD XML Catalog //&quot;
193 catalog=&quot;file:///usr/share/xml/docbook.xml&quot;/&gt;
194&lt;delegatePublic publicIdStartString=&quot;-//OASIS//ENTITIES DocBook XML&quot;
195 catalog=&quot;file:///usr/share/xml/docbook.xml&quot;/&gt;
196&lt;delegatePublic publicIdStartString=&quot;-//OASIS//DTD DocBook XML&quot;
197 catalog=&quot;file:///usr/share/xml/docbook.xml&quot;/&gt;
198&lt;delegateSystem systemIdStartString=&quot;http://www.oasis-open.org/docbook/&quot;
199 catalog=&quot;file:///usr/share/xml/docbook.xml&quot;/&gt;
200&lt;delegateURI uriStartString=&quot;http://www.oasis-open.org/docbook/&quot;
201 catalog=&quot;file:///usr/share/xml/docbook.xml&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]202...</pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]203<p>Delegation is the core features which allows to build a tree of catalogs,
204easier to maintain than a single catalog, based on Public Identifier, System
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]205Identifier or URI prefixes it instructs the catalog software to look up
206entries in another resource. This feature allow to build hierarchies of
207catalogs, the set of entries presented should be sufficient to redirect the
208resolution of all DocBook references to the specific catalog in
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]209<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all
210references for DocBook 4.2.1 to a specific catalog installed at the same time
211as the DocBook resources on the local machine.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]212<h3><a name="reference">How to tune catalog usage:</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]213<p>The user can change the default catalog behaviour by redirecting queries
214to its own set of catalogs, this can be done by setting the
215<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]216empty one should deactivate loading the default <code>/etc/xml/catalog</code>
217default catalog</p>
218<h3><a name="validate">How to debug catalog processing:</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]219<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will
220make libxml output debugging informations for each catalog operations, for
221example:</p>
222<pre>orchis:~/XML -&gt; xmllint --memory --noout test/ent2
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]223warning: failed to load external entity &quot;title.xml&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]224orchis:~/XML -&gt; export XML_DEBUG_CATALOG=
225orchis:~/XML -&gt; xmllint --memory --noout test/ent2
226Failed to parse catalog /etc/xml/catalog
227Failed to parse catalog /etc/xml/catalog
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]228warning: failed to load external entity &quot;title.xml&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]229Catalogs cleanup
230orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]231<p>The test/ent2 references an entity, running the parser from memory makes
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]232the base URI unavailable and the the &quot;title.xml&quot; entity cannot be loaded.
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]233Setting up the debug environment variable allows to detect that an attempt is
234made to load the <code>/etc/xml/catalog</code> but since it's not present the
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]235resolution fails.</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]236<p>But the most advanced way to debug XML catalog processing is to use the
237<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load
238catalogs and make resolution queries to see what is going on. This is also
239used for the regression tests:</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]240<pre>orchis:~/XML -&gt; ./xmlcatalog test/catalogs/docbook.xml \
241 &quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]242http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
243orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]244<p>For debugging what is going on, adding one -v flags increase the verbosity
245level to indicate the processing done (adding a second flag also indicate
246what elements are recognized at parsing):</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]247<pre>orchis:~/XML -&gt; ./xmlcatalog -v test/catalogs/docbook.xml \
248 &quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]249Parsing catalog test/catalogs/docbook.xml's content
250Found public match -//OASIS//DTD DocBook XML V4.1.2//EN
251http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
252Catalogs cleanup
253orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]254<p>A shell interface is also available to debug and process multiple queries
255(and for regression tests):</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]256<pre>orchis:~/XML -&gt; ./xmlcatalog -shell test/catalogs/docbook.xml \
257 &quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]258&gt; help
259Commands available:
260public PublicID: make a PUBLIC identifier lookup
261system SystemID: make a SYSTEM identifier lookup
262resolve PublicID SystemID: do a full resolver lookup
263add 'type' 'orig' 'replace' : add an entry
264del 'values' : remove values
265dump: print the current catalog state
266debug: increase the verbosity level
267quiet: decrease the verbosity level
268exit: quit the shell
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]269&gt; public &quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]270http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
271&gt; quit
272orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]273<p>This should be sufficient for most debugging purpose, this was actually
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]274used heavily to debug the XML Catalog implementation itself.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]275<h3>
276<a name="Declaring">How to create and maintain</a> catalogs:</h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]277<p>Basically XML Catalogs are XML files, you can either use XML tools to
278manage them or use <strong>xmlcatalog</strong> for this. The basic step is
279to create a catalog the -create option provide this facility:</p>
280<pre>orchis:~/XML -&gt; ./xmlcatalog --create tst.xml
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]281&lt;?xml version=&quot;1.0&quot;?&gt;
282&lt;!DOCTYPE catalog PUBLIC &quot;-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN&quot;
283 &quot;http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd&quot;&gt;
284&lt;catalog xmlns=&quot;urn:oasis:names:tc:entity:xmlns:xml:catalog&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]285orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]286<p>By default xmlcatalog does not overwrite the original catalog and save the
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]287result on the standard output, this can be overridden using the -noout
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]288option. The <code>-add</code> command allows to add entries in the
289catalog:</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]290<pre>orchis:~/XML -&gt; ./xmlcatalog --noout --create --add &quot;public&quot; \
291 &quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot; \
292 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]293orchis:~/XML -&gt; cat tst.xml
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]294&lt;?xml version=&quot;1.0&quot;?&gt;
295&lt;!DOCTYPE catalog PUBLIC &quot;-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN&quot; \
296 &quot;http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd&quot;&gt;
297&lt;catalog xmlns=&quot;urn:oasis:names:tc:entity:xmlns:xml:catalog&quot;&gt;
298&lt;public publicId=&quot;-//OASIS//DTD DocBook XML V4.1.2//EN&quot;
299 uri=&quot;http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]300&lt;/catalog&gt;
301orchis:~/XML -&gt; </pre>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]302<p>The <code>-add</code> option will always take 3 parameters even if some of
303the XML Catalog constructs (like nextCatalog) will have only a single
304argument, just pass a third empty string, it will be ignored.</p>
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]305<p>Similarly the <code>-del</code> option remove matching entries from the
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]306catalog:</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]307<pre>orchis:~/XML -&gt; ./xmlcatalog --del \
308 &quot;http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd&quot; tst.xml
309&lt;?xml version=&quot;1.0&quot;?&gt;
310&lt;!DOCTYPE catalog PUBLIC &quot;-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN&quot;
311 &quot;http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd&quot;&gt;
312&lt;catalog xmlns=&quot;urn:oasis:names:tc:entity:xmlns:xml:catalog&quot;/&gt;
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]313orchis:~/XML -&gt; </pre>
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]314<p>The catalog is now empty. Note that the matching of <code>-del</code> is
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]315exact and would have worked in a similar fashion with the Public ID
316string.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]317<p>This is rudimentary but should be sufficient to manage a not too complex
318catalog tree of resources.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]319<h3><a name="implemento">The implementor corner quick review of the
320API:</a></h3>
321<p>First, and like for every other module of libxml, there is an
322automatically generated <a href="html/libxml-catalog.html">API page for
323catalog support</a>.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]324<p>The header for the catalog interfaces should be included as:</p>
325<pre>#include &lt;libxml/catalog.h&gt;</pre>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]326<p>The API is voluntarily kept very simple. First it is not obvious that
327applications really need access to it since it is the default behaviour of
328libxml (Note: it is possible to completely override libxml default catalog by
329using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to
330plug an application specific resolver).</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]331<p>Basically libxml support 2 catalog lists:</p>
332<ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]333<li>the default one, global shared by all the application</li>
334<li>a per-document catalog, this one is built if the document uses the
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]335 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is
336 associated to the parser context and destroyed when the parsing context
337 is destroyed.</li>
338</ul>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]339<p>the document one will be used first if it exists.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]340<h4>Initialization routines:</h4>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]341<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be
342used at startup to initialize the catalog, if the catalog should be
343initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs()
344should be called before xmlInitializeCatalog() which would otherwise do a
345default initialization first.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]346<p>The xmlCatalogAddLocal() call is used by the parser to grow the document
347own catalog list if needed.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]348<h4>Preferences setup:</h4>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]349<p>The XML Catalog spec requires the possibility to select default
350preferences between public and system delegation,
351xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and
352xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should
353be forbidden, allowed for global catalog, for document catalog or both, the
354default is to allow both.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]355<p>And of course xmlCatalogSetDebug() allows to generate debug messages
356(through the xmlGenericError() mechanism).</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]357<h4>Querying routines:</h4>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]358<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic()
359and xmlCatalogResolveURI() are relatively explicit if you read the XML
360Catalog specification they correspond to section 7 algorithms, they should
361also work if you have loaded an SGML catalog with a simplified semantic.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]362<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but
363operate on the document catalog list</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]364<h4>Cleanup and Miscellaneous:</h4>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]365<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is
366the per-document equivalent.</p>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]367<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the
368first catalog in the global list, and xmlCatalogDump() allows to dump a
369catalog state, those routines are primarily designed for xmlcatalog, I'm not
370sure that exposing more complex interfaces (like navigation ones) would be
371really useful.</p>
Daniel Veillard9f7b84b2001-08-23 15:31:19 +0000[diff] [blame]372<p>The xmlParseCatalogFile() is a function used to load XML Catalog files,
373it's similar as xmlParseFile() except it bypass all catalog lookups, it's
374provided because this functionality may be useful for client tools.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]375<h4>threaded environments:</h4>
Daniel Veillardffb120d2001-08-23 00:52:23 +0000[diff] [blame]376<p>Since the catalog tree is built progressively, some care has been taken to
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]377try to avoid troubles in multithreaded environments. The code is now thread
378safe assuming that the libxml library has been compiled with threads
379support.</p>
380<p>
381<h3><a name="Other">Other resources</a></h3>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]382<p>The XML Catalog specification is relatively recent so there isn't much
MDT 2001 John Fleck04685002001-09-03 16:11:47 +0000[diff] [blame]383literature to point at:</p>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]384<ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]385<li>You can find an good rant from Norm Walsh about <a href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]386 need for catalogs</a>, it provides a lot of context informations even if
387 I don't agree with everything presented.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]388<li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]389 catalog proposal</a> from John Cowan</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]390<li>The <a href="http://www.rddl.org/">Resource Directory Description
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]391 Language</a> (RDDL) another catalog system but more oriented toward
392 providing metadata for XML namespaces.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]393<li>the page from the OASIS Technical <a href="http://www.oasis-open.org/committees/entity/">Committee on Entity
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]394 Resolution</a> who maintains XML Catalog, you will find pointers to the
395 specification update, some background and pointers to others tools
396 providing XML Catalog support</li>
Daniel Veillard35e937a2002-01-19 22:21:54 +0000[diff] [blame]397<li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate
398 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/
399 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on
400 the resources found on the system. Otherwise it will just create
401 ~/xmlcatalog and ~/dbkxmlcatalog and doing:
Daniel Veillardc575b992002-02-08 13:28:40 +0000[diff] [blame]402 <p><code>export XMLCATALOG=$HOME/xmlcatalog</code></p>
Daniel Veillard35e937a2002-01-19 22:21:54 +0000[diff] [blame]403<p>should allow to process DocBook documentations without requiring
404 network accesses for the DTd or stylesheets</p>
405</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]406<li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a
Daniel Veillard35e937a2002-01-19 22:21:54 +0000[diff] [blame]407 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems
408 to work fine for me too</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]409<li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog
410 manual page</a>
411</li>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]412</ul>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]413<p>If you have suggestions for corrections or additions, simply contact
414me:</p>
Daniel Veillard3f4c40f2002-02-13 09:19:28 +0000[diff] [blame]415<p><a href="bugs.html">Daniel Veillard</a></p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]416</td></tr></table></td></tr></table></td></tr></table></td>
417</tr></table></td></tr></table>
Daniel Veillarde7ead2d2001-08-22 23:44:09 +0000[diff] [blame]418</body>
419</html>