conditional multiple outputs

Hi,

I am trying to generate multiple output files in a single template (see
xsl file below). The scenario is the following:

1. I read elements <title> one after the other from a input file
"content.xml"
2. if the text of the element <title> begins with the substring "file 1",
then copy the element to the output file file1.xml, if it begins with
"file 2" then output to file2.xml, else copy the element to file3.xml.

The processor I use is Saxon B on .NET and XLST version is 2.0. But my
script does not work since I always have following error message:

E:\test\xsl>Transform -s:"e:\test\xsl\content.xml"
-xsl:"e:\test\xsl\import.xsl
Error at xsl:choose on line 8 of file:///e:/test/xsl/import.xsl:
  XTDE1490: Cannot write more than one result document to the same URI, or
write to a URI
  that has been read: file:/E:/test/xsl/file2.xml
Transformation failed: Run-time errors were reported



Here are the script and the input file content.xml:

<!--content.xml-->
<?xml version="1.0" encoding="UTF-8"?>
<groups>
        <group>
                <title>file 1 xxx </title>
                <title>file 2 efg </title>
        </group>
        <group>
                <title>file 2 xxx </title>
                <title>file 3 abc </title>
        </group>
        <group>
                <title>file 1 abc </title>
                <title>file 3 xyz </title>
        </group>
        <group>
                <title>file 2 zzz </title>
                <title>file 2 ihk </title>
        </group>
</groups>



<!--multipleOutput.xsl-->
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0">
        <xsl:output method="xml" indent="yes" encoding="utf-8"/>
        <xsl:template name="test" match="/">
                <xsl:for-each select="groups/group">
                        <xsl:for-each select="title">
                                <xsl:variable name="textOfTheElementTitle"
select="substring(./text(), 1, 6)"/>
                                <xsl:choose>
                                        <xsl:when
test="matches($textOfTheElementTitle,
'file 1', 'i')">
                                                <xsl:result-document
href="file1.xml">
                                                        <contentOfTitleElmt>
                                                                <xsl:value-of
select="./text()"/>
                                                        </contentOfTitleElmt>
                                                </xsl:result-document>
                                        </xsl:when>
                                        <xsl:when
test="matches($textOfTheElementTitle,
'file 2', 'i')">
                                                <xsl:result-document
href="file2.xml">
                                                        <contentOfTitleElmt>
                                                                <xsl:value-of
select="./text()"/>
                                                        </contentOfTitleElmt>
                                                </xsl:result-document>
                                        </xsl:when>
                                        <xsl:otherwise>
                                                <xsl:result-document
href="file3.xml">
                                                        <contentOfTitleElmt>
                                                                <xsl:value-of
select="./text()"/>
                                                        </contentOfTitleElmt>
                                                </xsl:result-document>
                                        </xsl:otherwise>
                                </xsl:choose>
                        </xsl:for-each>
                </xsl:for-each>
        </xsl:template>
</xsl:stylesheet>

Does somebody know why it does not work? Should I use another function
than xsl:result-document?

Many thanks in advance,
Regards

Horace