what are node set fragments and why are they ruining my life

see the minimal xsl and xml file below.

first off, nothing i've read in the spec or the various xsl tutorials
make any sense in defining what a node set fragment is.
they talk about things like "not being well-formed", but (a) i'm not
clear how one is able to produce something that isn't well-formed,
and (b) that doesn't match experience as this example shows.

here i've shown where the mere act of passing a node set (fragment)
through a call-template is enough to defile it.

here are the various outputs.

1. comment out first for-each, use xt
output is:
member 1

note that there is a result, but no xsl:message instructions are run

2. comment out first for-each, use saxon
output is:
member local-name=member, id=1
member local-name=member, id=2

note that there is no result, but the xsl:message instructions are run

3. leave in first for-each, use xt
output is:
cannot convert to node-set

4. leave in first for-each, use saxon
member local-name=member, id=1
member local-name=member, id=2
Error during source document processing
At xsl:for-each on line 32 of file:/d:/mda/projects/xmlhacks/xmlidl/test1.xsl: Cannot convert value [** RESULT TREE FRAGMENT **] to
a node-set

Thanks to anyone who can elucide this matter.

-mda

test1.xml

<root>
  <member id="1">member 1</member>
  <member id="2">member 2</member>
</root>


test1.xsl

<?xml version="1.0" ?>

<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:date="http://www.jclark.com/xt/java/java.util.Date"
  xmlns:xt="http://www.jclark.com/xt"
  xmlns:sxf="/com.icl.saxon.functions.Extensions"
  extension-element-prefixes="date xt sxf"
  exclude-result-prefixes="date sxf xt"
  >
  <xsl:output
     method="html"
     indent="yes"
     doctype-public="-//W3C//DTD HTML 4.0 Transitional//EN"
  />
  <xsl:strip-space elements="*"/>

  <xsl:template match="root">
    <xsl:variable name="members">
      <xsl:call-template name="get_members"/>
    </xsl:variable>
    <!-- why can't i use a variable? something about result tree fragments... -->

    <!-- comment this for-each out to avoid the runtime error
    <xsl:for-each select="$members">
      <xsl:message>member local-name=<xsl:value-of select="local-name(.)"/>, id=<xsl:value-of select="@id"/></xsl:message>
    </xsl:for-each>
    -->
    <xsl:value-of select="$members"/>
  </xsl:template>

  <xsl:template name="get_members">
    <xsl:variable name="result" select="*"/>
    <xsl:for-each select="$result">
      <xsl:message>member local-name=<xsl:value-of select="local-name(.)"/>, id=<xsl:value-of select="@id"/></xsl:message>
    </xsl:for-each>
    <!-- same thing as: <xsl:value-of select="$result"/> -->
    <xsl:value-of select="*"/>
  </xsl:template>

</xsl:stylesheet>



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