Nodes get new IDs in function?

Hey list,

still struggling with the level gap-infested ToC, but I think I
introduced a couple of functions, I'm now on the finish line:

<xsl:function name="o2e:heading-level" as="xs:integer">
    <xsl:param name="heading" as="element()"/>
    <xsl:value-of select="number(substring-after(local-name($heading), 'h'))"/>
</xsl:function>

<xsl:function name="o2e:parent-heading" as="element()*">
    <xsl:param name="heading" as="element()"/>
    <xsl:copy-of select="$heading/preceding-sibling::h:*[self::h:h1 or
self::h:h2 or self::h:h3 or self::h:h4 or self::h:h5 or
self::h:h6][o2e:heading-level(.) &lt;
o2e:heading-level($heading)][1]"/>
</xsl:function>

The problem is, it seems that nodes returned from the parent-heading()
function get different IDs than identical nodes in the source
document. Is this the specified behavior, i.e. functions construct new
nodes, which get new IDs?

For that reason this expression won't work:

following-sibling::h:*[self::h:h1 or self::h:h2 or self::h:h3 or
self::h:h4 or self::h:h5 or self::h:h6][o2e:parent-heading(.) is
current()]

Because the IDs won't match in the 'is' operator, even though I can
see the nodes are (look) identical. If I change the operator to '=' it
starts giving the expected results, but it is not good enough, as
there can be several heading elements with the same string value. Is
it possible to retain the original ID value somehow?

As for the source document, it could be any XHTML with any number and
order of headings, for example:

<h1 class="Heading_20_1 ">Free Culture - How Big Media Uses Technology
and the Law to Lock Down Culture and Control Creativity,Lawrence
Lessig</h1>
<h4 class="Heading_20_4 ">Attribution</h4>
<p>...</p>
<h3 class="Heading_20_3 ">Preface</h3>
<h4 class="Heading_20_4 ">[Preface]</h4>
<p>...</p>
<h3 class="Heading_20_3 ">INTRODUCTION</h3>
<p>...</p>

and so on

Martynas
odt2epub.com