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diff --git a/libxml2-2.9.10/doc/catalog.html b/libxml2-2.9.10/doc/catalog.html new file mode 100644 index 0000000..42be5e7 --- /dev/null +++ b/libxml2-2.9.10/doc/catalog.html @@ -0,0 +1,261 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css"> +TD {font-family: Verdana,Arial,Helvetica} +BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em} +H1 {font-family: Verdana,Arial,Helvetica} +H2 {font-family: Verdana,Arial,Helvetica} +H3 {font-family: Verdana,Arial,Helvetica} +A:link, A:visited, A:active { text-decoration: underline } +</style><title>Catalog support</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>Catalog support</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html">Home</a></li><li><a href="html/index.html">Reference Manual</a></li><li><a href="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html" style="font-weight:bold">Developer Menu</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="help.html">How to help</a></li><li><a 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href="https://gitlab.gnome.org/GNOME/libxml2/issues">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>Table of Content:</p><ol> + <li><a href="General2">General overview</a></li> + <li><a href="#definition">The definition</a></li> + <li><a href="#Simple">Using catalogs</a></li> + <li><a href="#Some">Some examples</a></li> + <li><a href="#reference">How to tune catalog usage</a></li> + <li><a href="#validate">How to debug catalog processing</a></li> + <li><a href="#Declaring">How to create and maintain catalogs</a></li> + <li><a href="#implemento">The implementor corner quick review of the + API</a></li> + <li><a href="#Other">Other resources</a></li> +</ol><h3><a name="General2" id="General2">General overview</a></h3><p>What is a catalog? Basically it's a lookup mechanism used when an entity +(a file or a remote resource) references another entity. The catalog lookup +is inserted between the moment the reference is recognized by the software +(XML parser, stylesheet processing, or even images referenced for inclusion +in a rendering) and the time where loading that resource is actually +started.</p><p>It is basically used for 3 things:</p><ul> + <li>mapping from "logical" names, the public identifiers and a more + concrete name usable for download (and URI). For example it can associate + the logical name + <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> + <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be + downloaded</p> + <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> + </li> + <li>remapping from a given URL to another one, like an HTTP indirection + saying that + <p>"http://www.oasis-open.org/committes/tr.xsl"</p> + <p>should really be looked at</p> + <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> + </li> + <li>providing a local cache mechanism allowing to load the entities + associated to public identifiers or remote resources, this is a really + important feature for any significant deployment of XML or SGML since it + allows to avoid the aleas and delays associated to fetching remote + resources.</li> +</ul><h3><a name="definition" id="definition">The definitions</a></h3><p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p><ul> + <li>the older SGML catalogs, the official spec is SGML Open Technical + Resolution TR9401:1997, but is better understood by reading <a href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from + James Clark. This is relatively old and not the preferred mode of + operation of libxml.</li> + <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML + Catalogs</a> is far more flexible, more recent, uses an XML syntax and + should scale quite better. This is the default option of libxml.</li> +</ul><p></p><h3><a name="Simple" id="Simple">Using catalog</a></h3><p>In a normal environment libxml2 will by default check the presence of a +catalog in /etc/xml/catalog, and assuming it has been correctly populated, +the processing is completely transparent to the document user. To take a +concrete example, suppose you are authoring a DocBook document, this one +starts with the following DOCTYPE definition:</p><pre><?xml version='1.0'?> +<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" + "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre><p>When validating the document with libxml, the catalog will be +automatically consulted to lookup the public identifier "-//Norman Walsh//DTD +DocBk XML V3.1.4//EN" and the system identifier +"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have +been installed on your system and the catalogs actually point to them, libxml +will fetch them from the local disk.</p><p style="font-size: 10pt"><strong>Note</strong>: Really don't use this +DOCTYPE example it's a really old version, but is fine as an example.</p><p>Libxml2 will check the catalog each time that it is requested to load an +entity, this includes DTD, external parsed entities, stylesheets, etc ... If +your system is correctly configured all the authoring phase and processing +should use only local files, even if your document stays portable because it +uses the canonical public and system ID, referencing the remote document.</p><h3><a name="Some" id="Some">Some examples:</a></h3><p>Here is a couple of fragments from XML Catalogs used in libxml2 early +regression tests in <code>test/catalogs</code> :</p><pre><?xml version="1.0"?> +<!DOCTYPE catalog PUBLIC + "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" + "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> +<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> + <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" + uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> +...</pre><p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are +written in XML, there is a specific namespace for catalog elements +"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this +catalog is a <code>public</code> mapping it allows to associate a Public +Identifier with an URI.</p><pre>... + <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" + rewritePrefix="file:///usr/share/xml/docbook/"/> +...</pre><p>A <code>rewriteSystem</code> is a very powerful instruction, it says that +any URI starting with a given prefix should be looked at another URI +constructed by replacing the prefix with an new one. In effect this acts like +a cache system for a full area of the Web. In practice it is extremely useful +with a file prefix if you have installed a copy of those resources on your +local system.</p><pre>... +<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" + catalog="file:///usr/share/xml/docbook.xml"/> +<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" + catalog="file:///usr/share/xml/docbook.xml"/> +<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" + catalog="file:///usr/share/xml/docbook.xml"/> +<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" + catalog="file:///usr/share/xml/docbook.xml"/> +<delegateURI uriStartString="http://www.oasis-open.org/docbook/" + catalog="file:///usr/share/xml/docbook.xml"/> +...</pre><p>Delegation is the core features which allows to build a tree of catalogs, +easier to maintain than a single catalog, based on Public Identifier, System +Identifier or URI prefixes it instructs the catalog software to look up +entries in another resource. This feature allow to build hierarchies of +catalogs, the set of entries presented should be sufficient to redirect the +resolution of all DocBook references to the specific catalog in +<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all +references for DocBook 4.2.1 to a specific catalog installed at the same time +as the DocBook resources on the local machine.</p><h3><a name="reference" id="reference">How to tune catalog usage:</a></h3><p>The user can change the default catalog behaviour by redirecting queries +to its own set of catalogs, this can be done by setting the +<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an +empty one should deactivate loading the default <code>/etc/xml/catalog</code> +default catalog</p><h3><a name="validate" id="validate">How to debug catalog processing:</a></h3><p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will +make libxml2 output debugging information for each catalog operations, for +example:</p><pre>orchis:~/XML -> xmllint --memory --noout test/ent2 +warning: failed to load external entity "title.xml" +orchis:~/XML -> export XML_DEBUG_CATALOG= +orchis:~/XML -> xmllint --memory --noout test/ent2 +Failed to parse catalog /etc/xml/catalog +Failed to parse catalog /etc/xml/catalog +warning: failed to load external entity "title.xml" +Catalogs cleanup +orchis:~/XML -> </pre><p>The test/ent2 references an entity, running the parser from memory makes +the base URI unavailable and the the "title.xml" entity cannot be loaded. +Setting up the debug environment variable allows to detect that an attempt is +made to load the <code>/etc/xml/catalog</code> but since it's not present the +resolution fails.</p><p>But the most advanced way to debug XML catalog processing is to use the +<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load +catalogs and make resolution queries to see what is going on. This is also +used for the regression tests:</p><pre>orchis:~/XML -> ./xmlcatalog test/catalogs/docbook.xml \ + "-//OASIS//DTD DocBook XML V4.1.2//EN" +http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd +orchis:~/XML -> </pre><p>For debugging what is going on, adding one -v flags increase the verbosity +level to indicate the processing done (adding a second flag also indicate +what elements are recognized at parsing):</p><pre>orchis:~/XML -> ./xmlcatalog -v test/catalogs/docbook.xml \ + "-//OASIS//DTD DocBook XML V4.1.2//EN" +Parsing catalog test/catalogs/docbook.xml's content +Found public match -//OASIS//DTD DocBook XML V4.1.2//EN +http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd +Catalogs cleanup +orchis:~/XML -> </pre><p>A shell interface is also available to debug and process multiple queries +(and for regression tests):</p><pre>orchis:~/XML -> ./xmlcatalog -shell test/catalogs/docbook.xml \ + "-//OASIS//DTD DocBook XML V4.1.2//EN" +> help +Commands available: +public PublicID: make a PUBLIC identifier lookup +system SystemID: make a SYSTEM identifier lookup +resolve PublicID SystemID: do a full resolver lookup +add 'type' 'orig' 'replace' : add an entry +del 'values' : remove values +dump: print the current catalog state +debug: increase the verbosity level +quiet: decrease the verbosity level +exit: quit the shell +> public "-//OASIS//DTD DocBook XML V4.1.2//EN" +http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd +> quit +orchis:~/XML -> </pre><p>This should be sufficient for most debugging purpose, this was actually +used heavily to debug the XML Catalog implementation itself.</p><h3><a name="Declaring" id="Declaring">How to create and maintain</a> catalogs:</h3><p>Basically XML Catalogs are XML files, you can either use XML tools to +manage them or use <strong>xmlcatalog</strong> for this. The basic step is +to create a catalog the -create option provide this facility:</p><pre>orchis:~/XML -> ./xmlcatalog --create tst.xml +<?xml version="1.0"?> +<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" + "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> +<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> +orchis:~/XML -> </pre><p>By default xmlcatalog does not overwrite the original catalog and save the +result on the standard output, this can be overridden using the -noout +option. The <code>-add</code> command allows to add entries in the +catalog:</p><pre>orchis:~/XML -> ./xmlcatalog --noout --create --add "public" \ + "-//OASIS//DTD DocBook XML V4.1.2//EN" \ + http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml +orchis:~/XML -> cat tst.xml +<?xml version="1.0"?> +<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ + "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> +<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> +<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" + uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> +</catalog> +orchis:~/XML -> </pre><p>The <code>-add</code> option will always take 3 parameters even if some of +the XML Catalog constructs (like nextCatalog) will have only a single +argument, just pass a third empty string, it will be ignored.</p><p>Similarly the <code>-del</code> option remove matching entries from the +catalog:</p><pre>orchis:~/XML -> ./xmlcatalog --del \ + "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml +<?xml version="1.0"?> +<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" + "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> +<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> +orchis:~/XML -> </pre><p>The catalog is now empty. Note that the matching of <code>-del</code> is +exact and would have worked in a similar fashion with the Public ID +string.</p><p>This is rudimentary but should be sufficient to manage a not too complex +catalog tree of resources.</p><h3><a name="implemento" id="implemento">The implementor corner quick review of the +API:</a></h3><p>First, and like for every other module of libxml, there is an +automatically generated <a href="html/libxml-catalog.html">API page for +catalog support</a>.</p><p>The header for the catalog interfaces should be included as:</p><pre>#include <libxml/catalog.h></pre><p>The API is voluntarily kept very simple. First it is not obvious that +applications really need access to it since it is the default behaviour of +libxml2 (Note: it is possible to completely override libxml2 default catalog +by using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to +plug an application specific resolver).</p><p>Basically libxml2 support 2 catalog lists:</p><ul> + <li>the default one, global shared by all the application</li> + <li>a per-document catalog, this one is built if the document uses the + <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is + associated to the parser context and destroyed when the parsing context + is destroyed.</li> +</ul><p>the document one will be used first if it exists.</p><h4>Initialization routines:</h4><p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be +used at startup to initialize the catalog, if the catalog should be +initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() +should be called before xmlInitializeCatalog() which would otherwise do a +default initialization first.</p><p>The xmlCatalogAddLocal() call is used by the parser to grow the document +own catalog list if needed.</p><h4>Preferences setup:</h4><p>The XML Catalog spec requires the possibility to select default +preferences between public and system delegation, +xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and +xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should +be forbidden, allowed for global catalog, for document catalog or both, the +default is to allow both.</p><p>And of course xmlCatalogSetDebug() allows to generate debug messages +(through the xmlGenericError() mechanism).</p><h4>Querying routines:</h4><p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() +and xmlCatalogResolveURI() are relatively explicit if you read the XML +Catalog specification they correspond to section 7 algorithms, they should +also work if you have loaded an SGML catalog with a simplified semantic.</p><p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but +operate on the document catalog list</p><h4>Cleanup and Miscellaneous:</h4><p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is +the per-document equivalent.</p><p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the +first catalog in the global list, and xmlCatalogDump() allows to dump a +catalog state, those routines are primarily designed for xmlcatalog, I'm not +sure that exposing more complex interfaces (like navigation ones) would be +really useful.</p><p>The xmlParseCatalogFile() is a function used to load XML Catalog files, +it's similar as xmlParseFile() except it bypass all catalog lookups, it's +provided because this functionality may be useful for client tools.</p><h4>threaded environments:</h4><p>Since the catalog tree is built progressively, some care has been taken to +try to avoid troubles in multithreaded environments. The code is now thread +safe assuming that the libxml2 library has been compiled with threads +support.</p><p></p><h3><a name="Other" id="Other">Other resources</a></h3><p>The XML Catalog specification is relatively recent so there isn't much +literature to point at:</p><ul> + <li>You can find a good rant from Norm Walsh about <a href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the + need for catalogs</a>, it provides a lot of context information even if + I don't agree with everything presented. Norm also wrote a more recent + article <a href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML + entities and URI resolvers</a> describing them.</li> + <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML + catalog proposal</a> from John Cowan</li> + <li>The <a href="http://www.rddl.org/">Resource Directory Description + Language</a> (RDDL) another catalog system but more oriented toward + providing metadata for XML namespaces.</li> + <li>the page from the OASIS Technical <a href="http://www.oasis-open.org/committees/entity/">Committee on Entity + Resolution</a> who maintains XML Catalog, you will find pointers to the + specification update, some background and pointers to others tools + providing XML Catalog support</li> + <li>There is a <a href="buildDocBookCatalog">shell script</a> to generate + XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ + directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on + the resources found on the system. Otherwise it will just create + ~/xmlcatalog and ~/dbkxmlcatalog and doing: + <p><code>export XML_CATALOG_FILES=$HOME/xmlcatalog</code></p> + <p>should allow to process DocBook documentations without requiring + network accesses for the DTD or stylesheets</p> + </li> + <li>I have uploaded <a href="ftp://xmlsoft.org/libxml2/test/dbk412catalog.tar.gz">a + small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems + to work fine for me too</li> + <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog + manual page</a></li> +</ul><p>If you have suggestions for corrections or additions, simply contact +me:</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html> |