XSLT xmlns on root only - xslt-1.0

Question

Want to add an xmlns declaration to the root only and I use this xml:
<Message>
</Message>
and xslt:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="/">
<xsl:element name="Element1" namespace="http://www.blablabla.com">
<xsl:element name="Element2">
<xsl:element name="Element3">Hmm</xsl:element>
</xsl:element>
<xsl:element name="Element4">
</xsl:element>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
The result is:
<Element1 xmlns="http://www.blablabla.com">
<Element2 xmlns="">
<Element3>Hmm</Element3>
</Element2>
<Element4 xmlns=""/>
</Element1>
I want only Element1 to have xmlns not the Element2, 4 or others.
I can make this way but that means to write for each element the variable name:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="vNS"
select="'http://www.blablabla'"/>
<xsl:template match="/">
<xsl:element name="Element1" namespace="{$vNS}">
<xsl:element name="Element2" namespace="{$vNS}">
<xsl:element name="Element3" namespace="{$vNS}">Hmm</xsl:element>
</xsl:element>
<xsl:element name="Element4" namespace="{$vNS}">
</xsl:element>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
How to do it?
Thanks.

Answer 1

Using xsl:element with namespaces requires you to indicate for all elements in which namespace they belong. It is easier to avoid using xsl:element when dealing with namespaces.
For example:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:bla="http://www.blablabla.com">
<xsl:output method="xml" version="1.0" encoding="UTF-8" omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="/">
<bla:Element1>
<Element2>
<Element3>Hmm</Element3>
</Element2>
<Element4 />
</bla:Element1>
</xsl:template>
</xsl:stylesheet>
This will create the required namespace on only the first element. You just have to declare the namespace into the stylesheet declaration and then you can use this namespace directly in the elements. Also your XSLT is more readable when avoiding xsl:element.