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xref — A cross reference to another part of the document
xref ::= EMPTY
| 
                         Name  | 
                     
                         Type  | 
                     
                         Default  | 
                  
| xrefstyle | CDATA | None | 
| endterm | IDREF | None | 
| linkend | IDREF | Required | 
               The XRef element forms a cross-reference from the location
               of the XRef to the element to which it points.  Unlike
               Link and the other cross-referencing elements, XRef
               is empty. The processing system has to generate appropriate cross-reference
               text for the reader.
               
            
Under ordinary circumstances, the xref
                  points to the some element with its
                  linkend attribute and the processing system
                  generates appropriate cross reference text. There are three
                  ways for the author to influence the generated text:
               
If the endterm attribute is specified
                           on xref, the
                           content of the element pointed to by endterm
                           will be used as the text of the cross-reference.
                           
                        
Otherwise, if the object pointed to has a
                           specified XRefLabel, the content of
                           that attribute will be used as the cross-reference text.
                           
                        
Finally, the author may specify a keyword (or other information) in the
                           xrefstyle attribute. Unlike
                           endterm and
                           xreflabel which have rigid semantics,
                           the content of the xrefstyle attribute is simply
                           additional information for the processing system. What effect it has, if any,
                           is dependent on the processing system.
                        
These elements contain xref:
                  application, attribution, bibliomisc, bridgehead, citation, citetitle, emphasis, entry, firstterm, foreignphrase, glosssee, glossseealso, glossterm, lineannotation, link, literallayout, lotentry, member, msgaud, olink, para, phrase, primary, primaryie, productname, programlisting, quote, refentrytitle, refpurpose, remark, screen, screeninfo, secondary, secondaryie, see, seealso, seealsoie, seeie, seg, segtitle, simpara, subtitle, synopsis, td, term, termdef, tertiary, tertiaryie, th, title, titleabbrev, tocback, tocentry, tocfront, ulink.
               
                        Endterm points to the element whose content
                        is to be used as the text of the link.
                        
                     
                        Linkend points to the target of the cross reference.
                        
                     
Consider the following example:
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<book><title>An Example Book</title>
<chapter id="ch01"><title>XRef Samples</title>
<para>
This paragraph demonstrates several features of
<sgmltag>XRef</sgmltag>.
</para>
<itemizedlist>
<listitem><para>A straight link generates the
cross-reference text: <xref linkend="ch02"/>.
</para></listitem>
<listitem><para>A link to an element with an
<sgmltag class="attribute">XRefLabel</sgmltag>:
<xref linkend="ch03"/>.
</para></listitem>
<listitem><para>A link with an
<sgmltag class="attribute">EndTerm</sgmltag>:
<xref linkend="ch04" endterm="ch04short"/>.
</para></listitem>
</itemizedlist>
</chapter>
<chapter id="ch02">
  <title>The Second Chapter</title>
  <para>Some content here</para>
</chapter>
<chapter id="ch03" xreflabel="Chapter the Third">
  <title>The Third Chapter</title>
  <para>Some content here</para>
</chapter>
<chapter id="ch04">
  <title>The Fourth Chapter</title>
  <titleabbrev id="ch04short">Chapter 4</titleabbrev>
  <para>Some content here</para>
</chapter>
</book>One reasonable rendering for the content of the first chapter of this book is the following:
               This paragraph demonstrates several features of
               XRef.
               
            
A straight link generates the cross-reference text: Chapter 2, “The Second Chapter”
A link to an element with an
                        XRefLabel:
                        Chapter the Third.
                        
                     
A link with an
                        EndTerm:
                        Chapter 4.
                        
                     
Of course, in an online system, these references would also be links to the appropriate chapters.
For additional examples, see also
               part.