This is an issue about the scope of global variables in conjunction
with imports and includes.

Scenario:
- two imported stylesheets (A) and (B) both include the same
  third stylesheet (C)
- stylesheet (C) has two references to variables:
  - the first references a variable in (A)
  - the second references a variable in (B)

Question:
Is this an error? Or are global variables of imported sheets merged
before inclusion of sheets is performed? Or does an other mechanism
apply?

Tested with MSXML 4.0/.NET and Xalan-J (an older version unfortunately):
Those processors allow such a scenario.

Libxslt reports an error here.

Example:

"multi.xsl" - the main sheet
-----------
<?xml version='1.0'?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:import href="multi-imp.xsl"/>
	<xsl:include href="multi-inc.xsl"/>
	<xsl:variable name="var-1" select="'value-1'"/>
	<xsl:template match="/">
		<foo>
			<xsl:apply-templates/>
		</foo>
	</xsl:template>
</xsl:stylesheet>

"multi-imp.xsl" - the imported sheet
---------------
<?xml version='1.0'?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:include href="multi-inc.xsl"/>
	<xsl:variable name="var-2" select="'value-2'"/>	
	<xsl:template match="bar">
		<bar>
			<xsl:apply-templates/>
		</bar>
	</xsl:template>
</xsl:stylesheet>

"multi-inc.xsl" - the sheet included by both above sheets
---------------
<?xml version='1.0'?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:template match="zoo">
		<zoo attr-1="{$var-1}" attr-2="{$var-2}">
			<xsl:apply-templates/>
		</zoo>
	</xsl:template>
</xsl:stylesheet>

"test.xml" - the input document
<?xml version="1.0"?>
<foo><bar><zoo/></bar></foo>

result of xsltproc
------------------

>xsltproc multi.xsl ..\test.xml
runtime error: file multi-inc.xsl line 4 element zoo
unregistered variable var-1
xmlXPathCompiledEval: evaluation failed
runtime error: file multi-inc.xsl line 4 element zoo
unregistered variable var-2
xmlXPathCompiledEval: evaluation failed
<?xml version="1.0"?>
<foo><bar><zoo attr-1="runtime error" attr-2="runtime error"/></bar></foo>

Result of other processors
--------------------------

<?xml version='1.0' ?>
<foo><bar><zoo attr-2="value-2" attr-1="value-1"/></bar></foo>