Xpath related to following-sibling and preceding-sibling

I have the following example XML data with the desired output:

<Block id="block1">
<BlockContent>

<Para>This is para 1 in group 1</Para>
<Para>This is para 2 in group 1</Para>

<list><li>List item 1</li><li>List item 2</li></list>

<Para>This is para 1 in group 2</Para>
<Para>This is para 2 in group 2</Para>
<Para>This is para 3 in group 2</Para>
<Para>This is para 4 in group 2</Para>

</BlockContent>
</Block>

With the following desired output:

<description id="Block1_P1">
<p>This is para 1 in group 1</p>
<p>This is para 2 in group 1</p>
</description>

<list> .... </list>

<description id="Block1_P4">
<p>This is para 1 in group 2</p>
<p>This is para 2 in group 2</p>
<p>This is para 3 in group 2</p>
<p>This is para 4 in group 2</p>
</description>

I have the following portion of the XSLT, which generates...

<description id="Block1_P1">
<p>This is para 1 in group 1</p>
<p>This is para 2 in group 1</p>
<p>This is para 1 in group 2</p>
<p>This is para 2 in group 2</p>
<p>This is para 3 in group 2</p>
<p>This is para 4 in group 2</p></description>
<list> .... </list>

I know that I should have a check for a following-sibling that is not a
Para, but as yet I have not been able to come up with the correct Xpath
expression to complete this. Any suggestions? Thanks!

<xsl:for-each
select="//BlockContent/Para|//BlockContent/List|//BlockContent/Table">

        <!-- PARAs -->
        <xsl:if test="self::Para">      

                <xsl:choose>

                        <!-- When the preceding sibling was a para, then
the description element has already been established
                               and the para was appended into the
description element in a previous for loop; don't want to write
                               it out again -->
                        <xsl:when test="preceding-sibling::Para">
                        </xsl:when>

                        <!-- Otherwise, establish the description
element and put all consecutive paras within it as a chunk -->
                        <xsl:otherwise>
                                <xsl:call-template
name="FormatXMLOutput"/>

                                <xsl:element name="description">

                                        <xsl:attribute
name="identifier">
                                                <xsl:value-of
select="ancestor::Block[1]/@ID"/>
                                                <xsl:text>_P</xsl:text>
                                                <xsl:number count="Para"
from="BlockContent" level="single"/>
                                        </xsl:attribute>

                                        <xsl:call-template
name="FormatXMLOutput"/>

                                        <xsl:element name="p">
                                                <xsl:apply-templates/>
                                        </xsl:element>

                                        <!-- Now loop through all of the
siblings of the Para so that all consecutive paras are "chunked"
together in 
                                              the description element.
Note that the siblings are defined as on the same level so if there was
a list
                                              between this para and the
previous sibling para, then you don't want this in the same description
                                              element "chunk" -->

                                        <xsl:for-each
select="following-sibling::Para">
                                                <xsl:element name="p">
        
<xsl:apply-templates/>
                                                </xsl:element>
                                        </xsl:for-each>


                                </xsl:element>

                        </xsl:otherwise>

                </xsl:choose>                                   

        </xsl:if>  

Etc. specifically dealing with lists, tables, etc.

Thanks!


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