"Entity 'larr' not defined" in DocBook 5

Question

xsltproc complains "Entity 'larr' not defined'" when I try to use a plain left arrow (←, i.e. ←) which I don't see in any of the DocBook 5 entity lists. What do I need to include to get it to work?

My current XSL is:

<?xml version='1.0'?>
<xsl:stylesheet  
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

<xsl:import href="/usr/share/sgml/docbook/xsl-stylesheets/html/docbook.xsl"/>

<xsl:output method="html"
            encoding="UTF-8"
            indent="no"/>
<xsl:param name="html.stylesheet" select="'main.css'"/>
<xsl:param name="generate.toc">
  book      toc,title
</xsl:param>
<xsl:param name="glossterm.auto.link" select="1"/>

</xsl:stylesheet>

...and the docbook file starts merely with:

<book xmlns:xl="http://www.w3.org/1999/xlink">

...after which I go straight into the title and chapter tags.

Do I need to link to something else to get the "larr" entity, or is it simply cut out from DocBook 5?

Answer 1

It is not the XSLT stylesheet that is causing your problem (except if you used ← in the XSLT code, but did not show it). I assume you are using the ← entity in the input XML document.

Can you add an entity declaration at the top of your XML file?

<?xml version="1.0" standalone="yes" ?>    
<!DOCTYPE book [
  <!ENTITY larr "&#x2190;">
]>
<book/>

I'm not familiar with Docbook, but this page seems to suggest that's possible.

There are a few versions of this arrow, represented by different Unicode characters.