How to create html list from flat xml file using XSLT

I am looking for a clean way to do the following using XSLT.

Convert this source:

<para>blah blah</para>
<list>num1</list>
<list>num2</list>
<list>num3</list>
<para>blah blah</para>
<list>num1</list>
<list>num2</list>
<para>blah blah blah blah blah</para>

To this output:

<p>blah blah</p>
<ol>
    <li>num1</li>
    <li>num2</li>
    <li>num3</li>
</ol>
<p>blah blah</p>
<ol>
    <li>num1</li>
    <li>num2</li>
</ol>
<p>blah blah blah blah blah</p>

Keep in mind I do not know exactly how many <list>'s there will be.

So far I have this:

<xsl:template match="para">
    <p><xsl:value-of select="." /></p>
</xsl:template>

<xsl:template match="list">
    <ol><li><xsl:value-of select="." /></li></ol>
</xsl:template>

But my output looks like this:

<p>blah blah</p>    
<ol><li>num1</li></ol>
<ol><li>num2</li></ol>
<ol><li>num3</li></ol>
<p>blah blah</p>
<ol><li>num1</li></ol>
<ol><li>num2</li></ol>
<p>blah blah blah blah blah</p>

I know why I am getting duplicate <ol> elements, but I do not know how to stop it. Quite a brain teaser.

Any help would be greatly appreciated.

Solution

XSLT 2.0 has tools especially for this kind of Operations:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="xml">
        <xsl:for-each-group select="*" group-adjacent="boolean(self::list)">
            <xsl:choose>
                <xsl:when test="current-grouping-key()">
                    <ol>
                        <xsl:apply-templates select="current-group()"/>
                    </ol>
                </xsl:when>
                <xsl:otherwise>
                    <xsl:apply-templates select="current-group()"/>
                </xsl:otherwise>
            </xsl:choose>
        </xsl:for-each-group>
    </xsl:template>
    <xsl:template match="para">
        <p>
            <xsl:apply-templates/>
        </p>
    </xsl:template>
    <xsl:template match="list">
        <li>
            <xsl:apply-templates/>
        </li>
    </xsl:template>
</xsl:stylesheet>

With this XML:

<xml>
    <para>blah blah</para>
    <list>num1</list>
    <list>num2</list>
    <list>num3</list>
    <para>blah blah</para>
    <list>num1</list>
    <list>num2</list>
    <para>blah blah blah blah blah</para>
</xml>

You'll get the desired Output:

<p>blah blah</p>
<ol>
    <li>num1</li>
    <li>num2</li>
    <li>num3</li>
</ol>
<p>blah blah</p>
<ol>
    <li>num1</li>
    <li>num2</li>
</ol>
<p>blah blah blah blah blah</p>

You should read up on for-each-group at http://www.w3.org/TR/xslt20/#xsl-for-each-group