Hi Michael,

Thank-you for both of your responses very informative.

> Now for some reason you have chosen to use XSLT 1.0 rather than XSLT 2.0.
> That makes the problem no fun at all. If you really have to use XSLT 1.0,

Unfortunately I can not find a python library to support XSLT 2.0. The
library I am using only supports 1.0. I have written a large chunk of
code already so I have to stay with 1.0 only for now.

>     <xsl:variable name="ig" select="$doc//intergreen[from = $x and to =
> $y]"/>

When using XSLT 1.0 I got various error messages with the above syntax.
XPath error : Invalid expression
if (exists($ig)) then $ig/length else 0
                 ^

Just using the exists statement I got:-
xmlXPathCompOpEval: function exists not found

However I managed to work around this by looking at the string-length.
Working solution:-

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<tt>
<i>&#160;</i>
<xsl:for-each select="//traffic_signals/site/phases/phase">
 <i>&#160;<xsl:value-of select="letter" />&#160;</i>
</xsl:for-each>
 <i>&#160;
</i>
<xsl:for-each select="//traffic_signals/site/phases/phase">
 <xsl:variable name="row" select="letter"/>
 <i><xsl:value-of select="letter" /></i>
 <xsl:for-each select="//traffic_signals/site/phases/phase">
    <xsl:variable name="col" select="letter"/>
    <xsl:variable name="ig"
select="//traffic_signals/site/intergreens/intergreen[from=$row and
to=$col]/length"/>
    <xsl:if test="string-length($ig) &gt; 1" >
       <b><xsl:value-of select="$ig" />&#160;</b>
    </xsl:if>
    <xsl:if test="string-length($ig) &gt; 0" >
       <b>&#160;<xsl:value-of select="$ig" />&#160;</b>
    </xsl:if>
    <xsl:if test="string-length($ig) &lt; 1" >
       <xsl:if test="$row = $col" >
         <b>&#160;X&#160;</b>
       </xsl:if>
       <xsl:if test="$row != $col" >
         <b>&#160;-&#160;</b>
       </xsl:if>
    </xsl:if>
 </xsl:for-each>
 <i>&#160;
</i>
</xsl:for-each>
</tt>
</xsl:template>
</xsl:stylesheet>


Thanks for the help and feedback.

Regards,
Brendan M. Sleight