Modifying namespace definitions in xs:schema elements

Hi,

given an XML Schema, I should split this schema into two parts,
according to properties of elements and complex/simpleTypes.
Basically, I've succeeded to do this, using a couple of XSLT
transformations. But...

The original schema contains <xs:schema ... xmlns="a.b"
targetNamespace="a.b" ...>. I would like to modify this for one of the
results of the filtering, to become, e.g., xmlns="a.b.c"
targetNamespace="a.b.c". (The ultimate goal is to separate the
definitions made by the splt schemas into two different namespaces.)

Exploring the set of attributes in xs:schema (by <xsl:choose>
<xsl:when test="true()"> <xsl:value-of
select="concat(namespace-uri(),local-name())"/>...) has shown me that
the namespace definitions (xmlns="...") are not passed to template
processing.

Does this mean that what I want to be done cannot be achieved at all,
using XSLT techniques?

Thanks
-W