I am a beginner in XSLT.

I have an input XML file and a requiredelement.xml file which tells me the name of the elements that should be there in the output.

input.xml
<Root>
    <M1>
        <Element1>
            <Citizenship>aaaaaaaaa</Citizenship>
            <Phone a="b">phonenumber</Phone>
            <EmailAddress>email</EmailAddress>
        </Element1>
        <Element2>
            <Element2_2>Some data</Element2_2>
        </Element2>
        <Element3>data3</Element3>
        <Element4>data4</Element4>
        <Element5>data5</Element5>
        <Element6>data6</Element6>
        <Element7>data7</Element7>
        <Element8>data8</Element8>
        <Element9>data9</Element9>
    </M1>
</Root>

requiredelemnt.xml
<OutputElements>
        <segment>Element1</segment>
        <segment>Element6</segment>
</OutputElements>

The desired output
<Root>
    <M1>
        <Element1>
            <Citizenship>aaaaaaaaa</Citizenship>
            <Phone a="b">phonenumber</Phone>
            <EmailAddress>email</EmailAddress>
        </Element1>
        <Element6>data6</Element6>
    </M1>
</Root>


The XSL I am trying ( I know its wrong, but this as far as I can get )
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions" xmlns:xdt="http://www.w3.org/2005/xpath-datatypes">
    <xsl:template match="/">
        <xsl:for-each select="document('requiredelemnt.xml.xml')//segment">
            <xsl:apply-templates select=".">
                <xsl:with-param name="segvalue">
                    <xsl:value-of select="."/>
                </xsl:with-param>

            </xsl:apply-templates>
                        Here1
                </xsl:for-each>
    </xsl:template>
    <xsl:template match="segment">
        <xsl:param name="segvalue">localvalue</xsl:param>
        <xsl:copy-of select="$segvalue"/>
        Here 2 .. Value = <xsl:value-of select="$segvalue"/>
    </xsl:template>
</xsl:stylesheet>

The actual output that I am getting:
<?xml version="1.0" encoding="UTF-8"?>

        Here 2 .. Value = Element1
                        Here1


        Here 2 .. Value = Element6
                        Here1



Can you please help to correct or point me if I am totally off the mark.

Thanks

I would tackle this using two template rules: an identity copy rule that matches elements in the main document that are named in the second document, and a pass-through rule that matches elements not so named.

<xsl:template match="*[document('....')/x/y/z = name()]">
 <xsl:copy>
   <xsl:apply-templates/>
 </xsl:copy>
</xsl:template>

<xsl:template match="*">
  <xsl:apply-templates/>
</xsl:template>

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Thanks a lot.. I could build my XSL based on your suggestions. I wanted the root element and its one subelement from the source and then filter based on my requiredelements.xml so here is the XSL
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions" xmlns:xdt="http://www.w3.org/2005/xpath-datatypes">
<xsl:output method="xml"/>
    <xsl:template match="/*|/*/*">
        <xsl:copy>
         <xsl:copy-of select="@*"/>
        <xsl:apply-templates mode="copy"/>
            <xsl:apply-templates/>
        </xsl:copy>
    </xsl:template>
    <xsl:strip-space elements="*"/>
    <xsl:template match="*[document('v1.xml')//segment = name()] ">
        <xsl:copy>
            <xsl:copy-of select="@*|node()"/>
            <xsl:apply-templates mode="copy"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="*">
        <xsl:apply-templates/>
    </xsl:template>
</xsl:stylesheet>

Thanks Michael for your previous answer.
Just a small question. In the previous XSL, I am trying to do a case insensitive match by having the following XSL, but I get the error
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fo="http://www.w3.org/1999/XSL/Format" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions" xmlns:xdt="http://www.w3.org/2005/xpath-datatypes">
<xsl:variable name="reqelm" select="document('v1.xml')"/>
<xsl:output method="xml"/>
    <xsl:template match="/*|/*/*">
        <xsl:copy>
         <xsl:copy-of select="@*"/>
        <xsl:apply-templates mode="copy"/>
            <xsl:apply-templates/>
        </xsl:copy>
    </xsl:template>
    <xsl:strip-space elements="*"/>
<xsl:template match="*[lower-case($reqelm//segment)=lower-case(name())] ">
<xsl:copy>
            <xsl:copy-of select="@*|node()"/>
            <xsl:apply-templates mode="copy"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="*">
        <xsl:apply-templates/>
    </xsl:template>
</xsl:stylesheet>

The error is :
XPathParserException: The function 'lower-case' was not found.
pattern = '*[lower-case($reqelm//segment)=lower-case(name())] ' Remaining tokens are: ( 'lower-case' '(' '$' 'reqelm' '/' '/' 'segment' ')' '=' 'lower-case' '(' 'name' '(' ')' ')' ']') (t5.xsl, line 12, column 76)

I tried to replace the lower-case() with matches() but same problem.

Which processor are you using, very few support version 2.0, which lower-case() needs?
In version 1.0 you can use translate(string, from, to) and provide the appropriate alphabet strings for the last two parameters. This works with ASCII characters only though.

--

Joe (Microsoft MVP - XML)

Thanks Joe.
I am using Xalan version 1.10.0. so its not XSLT 2 I guess.

However when I tried to use translate in the match, I only get match on the first element
In the above example, I change the match line to
<xsl:template match="*[ translate($reqelm//segment, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')=
    translate(name(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')
    ] ">

I get the case insensitive match but only first element in ,my output. So the output I am getting now is
<Root>
    <M1>
        <Element1>
            <Citizenship>aaaaaaaaa</Citizenship>
            <Phone a="b">phonenumber</Phone>
            <EmailAddress>email</EmailAddress>
        </Element1>
    </M1>
</Root>
The expected output was
<Root>
    <M1>
        <Element1>
            <Citizenship>aaaaaaaaa</Citizenship>
            <Phone a="b">phonenumber</Phone>
            <EmailAddress>email</EmailAddress>
        </Element1>
        <Element6>data6</Element6>
    </M1>
</Root>

Any clue ?