Processing instructions

Hello, 
I'd like to manage PI with xsl (xalan). PIs are the history of the xml file.
I'd like to transform :
<p>bla1 bla1 bla1 bla1 
    <?Pub Tag atict:add user="toto" time="1098263343"?>adding texte
    <?Pub Caret?>
    <?Pub /atict:add?>bla1 bla1 bla1 </p>
to
<p>bla1 bla1 bla1 bla1 adding texte bla1 bla1 bla1 

and i'd like to transform :
<p>bla1 bla1 <?Pub Tag atict:del user="lanic" time="1098263158"?>removed text<?Pub /atict:del?><?Pub Caret?> bla1 bla1 </p>
to
<p>bla1 bla1 bla1 bla1 </p>

and especially :
<para>
    <p>bla bla bla bla</p>
    <?Pub Tag atict:join1 ref="4" user="lanic" time="1098264249"?>
        </para>
        <para>
    <?Pub Tag atict:join2 ref="4" user="lanic" time="1098264249"?><?Pub Caret?>
    <p>bla1 bla1 bla1 bla1 bla1 bla1 bla1 </p>
</para>
to
<para>
    <p>bla bla bla bla</p>
     <p>bla1 bla1 bla1 bla1 bla1 bla1 bla1 </p>
</para>

thank you for your help