XSLT: How to remove synonymous namespaces - xslt

Question

I have a large collection of XML files which I need to transform using XSLT. The problem is that many of these files were hand-written by different people and they do not use consistent names to refer to the schemas. For example, one file might use:
xmlns:itemType="http://example.com/ItemType/XSD"
where another might use the prefix "it" instead of "itemType":
xmlns:it="http://example.com/ItemType/XSD"
If that's not bad enough, there are several files which use two or three synonyms for the same thing!
<?xml version="1.0"?>
<Document
xmlns:it="http://example.com/ItemType/XSD"
xmlns:itemType="http://example.com/ItemType/XSD"
xmlns:ItemType="http://example.com/ItemType/XSD"
...
(there's clearly been a lot of cutting and pasting going on)
Now, because the pattern matching in the XSLT file appears to work on the namespace prefix (as opposed to the schema it relates to) the pattern only matches one of the variants. So if I write something like:
<xsl:template match="SomeNode[#xsi:type='itemType:SomeType']">
...
</xsl:template>
Then it only matches a subset of the cases that I want it to.
Question 1: Is there any way to get the XSLT to match all the variants?
Question 2: Is there any way to remove the duplicates so all the output files use consistent naming?
I naïvely tried using "namespace-alias" but I guess I've misunderstood what that does because I can't get it to do anything at all - either match all the variants or affect the output XML.
<?xsl:stylesheet
version="1.0"
...
xmlns:it="http://example.com/ItemType/XSD"
xmlns:itemType="http://example.com/ItemType/XSD"
xmlns:ItemType="http://example.com/ItemType/XSD"
...
<xsl:output method="xml" indent="yes"/>
<xsl:namespace-alias stylesheet-prefix="it" result-prefix="ItemType"/>
<xsl:namespace-alias stylesheet-prefix="itemType" result-prefix="ItemType"/>

Answer 1

Attribute values or text nodes won't be cast to QName unless you explicitly say so. Although this is only posible in XSLT/XPath 2.0
In XSLT/XPath 1.0 you must do this "manually":
<xsl:template match="SomeNode">
<xsl:variable name="vPrefix" select="substring-before(#xsi:type,':')"/>
<xsl:variable name="vNCName"
select="translate(substring-after(#xsi:type,$vPrefix),':','')"/>
<xsl:if test="namespace::*[
name()=$vPrefix
] = 'http://example.com/ItemType/XSD'
and
$vNCName = 'SomeType'">
<!-- Content Template -->
<xsl:if>
</xsl:template>
Edit: All in one pattern (less readable, maybe):
<xsl:template match="SomeNode[
namespace::*[
name()=substring-before(../#xsi:type,':')
] = 'http://example.com/ItemType/XSD'
and
substring(
concat(':',#xsi:type),
string-length(#xsi:type) - 7
) = ':SomeType'
]">
<!-- Content Template -->
</xsl:template>

Answer 2

In XSLT 2.0 (whether or not you use schema-awareness) you can write the predicate as [#xsi:type=xs:QName('it:SomeType')] where "it" is the prefix declared in the stylesheet for this namespace. It doesn't have to be the same as the prefix used in the source document.
Of course matching of element and attribute names (as distinct from QName-valued content) uses namespace URIs rather than prefixes in both XSLT 1.0 and XSLT 2.0.