Added use-id-as-filename parameter

src/guide/xml/ch02.xml

@@ -709,6 +709,21 @@ chunks.</para>
 navigation aids are constructed.</para>
 </listitem>
 </varlistentry>
+<varlistentry><term><parameter>use-id-as-filename</parameter></term>
+<listitem>
+<para>If this parameter <glossterm>is true</glossterm>, the <tag class="attribute">xml:id</tag>
+on a chunk will be used to construct the filename for that chunk. You can also control
+the chunk filename on a per-chunk basis with the 
+<literal>db</literal> processing instruction
+<indexterm>
+<primary>db processing instruction</primary>
+</indexterm> using the <literal>filename</literal><indexterm>
+<primary>db processing instruction</primary>
+<secondary>filename pseudo-attribute</secondary>
+</indexterm> pseudo-attribute.</para>
+</listitem>
+</varlistentry>
+
 </variablelist>
 
 <section xml:id="chunk-navigation">

src/guide/xml/changelog.xml

@@ -54,6 +54,11 @@ the combination of options. See <xref linkend="verbatim-environments"/>.</para>
 </listitem>
 </orderedlist>
 </listitem>
+<listitem>
+<para>Added <parameter>use-id-as-filename</parameter> parameter. If true,
+the <tag class="attribute">xml:id</tag> value of a chunk will be used as the
+chunk filename.</para>
+</listitem>
 </itemizedlist>
 </section>
 

src/guide/xml/ref-params.xml

@@ -5877,4 +5877,25 @@ The default language only applies to <tag>programlisting</tag> elements.</para>
 </refsection>
 </refentry>
 
+<refentry>
+  <refmeta>
+    <fieldsynopsis>
+      <type>xs:string</type>
+      <varname>use-id-as-filename</varname>
+      <initializer>'false'</initializer>
+    </fieldsynopsis>
+    <refmiscinfo class="version">2.5.0</refmiscinfo>
+  </refmeta>
+  <refnamediv>
+    <refpurpose>Use id as filename when chunking</refpurpose>
+  </refnamediv>
+<refsection>
+<title>Description</title>
+
+<para>If this parameter <glossterm>is true</glossterm>, when a document is being
+chunked, the <tag class="attribute">xml:id</tag> of a chunk will be used as the filename
+unless a processing instruction overrides it.</para>
+</refsection>
+</refentry>  
+
 </reference>

src/main/xslt/modules/chunk.xsl

@@ -140,6 +140,9 @@
     <xsl:when test="f:pi($node/db:info, 'basename')">
       <xsl:sequence select="f:pi($node/db:info, 'basename') || $html-extension"/>
     </xsl:when>
+    <xsl:when test="$node/@xml:id and f:is-true($use-id-as-filename)">
+      <xsl:sequence select="$node/@xml:id || $html-extension"/>
+    </xsl:when>
     <xsl:otherwise>
       <xsl:variable name="name" as="xs:string?">
         <xsl:apply-templates select="$node" mode="m:chunk-filename"/>