Hi,

I have following input XML structure, this is simplified:

<policy-rules>
  <fw-rule-order>
     fwrule3
     fwrule1
     fwrule2
  </fw-rule-order>
  <fw-rules>
     <rule name="fwrule1">
        <direction>out</direction>
        <action>pass<action>
        <remote>192.168.129.31</remote>
        <local>192.168.129.67</local>
     </rule>
     <rule name="fwrule2">
        <direction>in</direction>
        <action>drop<action>
        <remote>192.168.129.32</remote>
        <local>192.168.129.67</local>
     </rule>
     <rule name="fwrule3">
        <direction>out</direction>
        <action>pass<action>
        <remote>192.168.129.33</remote>
        <local>192.168.129.67</local>
     </rule>
  </fw-rules>
</policy-rules>

XML transformation in XSLT 1.0
<!-- Global variables -->
<xsl:variable name="rule-order">
  <xsl:value-of select="normalize-space(/policy-rules/fw-rule-order)"/>
</xsl:variable>

<xsl:template match="/">
  <policy>
     <xsl:apply-templates select="//fw-rules/rule"/>
  </policy>
</xsl:template>

<xsl:template match="//fw-rules/rule">
  <xsl:variable name="precedence">
     <xsl:call-template name="determineprecedence">
        <xsl:with-param name="string" select="$rule-order"/>
        <xsl:with-param name="value" select="@name"/>
     </xsl:call-template>
  </xsl:variable>
  <rule type="{action}" precedence="{$precedence}">}">
      <xsl:choose>
         <xsl:when test="direction='in'">
            <src>
               <xsl:apply-templates select="remote"/>
            </src>
            <dst>
               <xsl:apply-templates select="local"/>
            </dst>
         </xsl:when>
         <xsl:otherwise>
            <src>
               <xsl:apply-templates select="local"/>
            </src>
            <dst>
               <xsl:apply-templates select="remote"/>
            </dst>
         </xsl:otherwise>
      </xsl:choose>
  </rule>
</xsl:template>

<xsl:template match="remote">
  <xsl:value-of select="."/>
</xsl:template>

<xsl:template match="local">
  <xsl:value-of select="."/>
</xsl:template>

<!-- Named templates -->
<xsl:template name="determineprecedence">
  <xsl:param name="string"/>
  <xsl:param name="value"/>
  <!-- Returns the precedence of the rule -->
</xsl:template>

Output without sorting, after XSLT processor recursion:
<policy>
 <rule type="pass" precedence="1">
    <src>192.168.129.67</src>
    <dst>192.168.129.31</dst>
 </rule>
 <rule type="drop" precedence="2">
    <src>192.168.129.32</src>
    <dst>192.168.129.67</dst>
 </rule>
 <rule type="pass" precedence="0">
    <src>192.168.129.67</src>
    <dst>192.168.129.33</dst>
 </rule>
</policy>

Desired output:
<policy>
 <rule type="pass" precedence="0">
    <src>192.168.129.67</src>
    <dst>192.168.129.33</dst>
 </rule>
 <rule type="pass" precedence="1">
    <src>192.168.129.67</src>
    <dst>192.168.129.31</dst>
 </rule>
 <rule type="drop" precedence="2">
    <src>192.168.129.32</src>
    <dst>192.168.129.67</dst>
 </rule>
</policy>

I have been looking for some examples of the <xsl:sort> use. But I haven't catched any examples how this could be solved. This problem is only cosmetic, because of the precedence attribute. If there are many rules it is more comfortable to read the output file, if it is sorted by the precedence attribute as shown above.

I'm wondering if it is possible apply some kind of post-sorting in the output tree structure, before it is outputted to XML file? If there exists some sorting examples in the web, please point it out to me.

Atleast one solution could be forcing the apply of '//fw-rules/rule' template in the order <fw-rule-order> specifies.

If I understand what should be the result you're after, then this
transformation:

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<!-- Global variables -->
<xsl:variable name="vDg" select="'0123456789 '"/>

<xsl:variable name="rule-order">
 <xsl:value-of select="normalize-space(/policy-rules/fw-rule-order)"/>
</xsl:variable>

<xsl:variable name="vnruleOrder"
  select="translate($rule-order, translate($rule-order, $vDg,''), '')"
/>

<xsl:template match="policy-rules">
  <policy>
    <xsl:apply-templates select="fw-rules/rule">
      <xsl:sort data-type="number" select=
        "string-length(
                  substring-before($vnruleOrder,
                                   translate(@name,
                                             translate(@name, $vDg,''),
                                             ''
                                             )
                                   )
                       )"
      />
    </xsl:apply-templates>
  </policy>
</xsl:template>

<xsl:template match="fw-rules/rule">
  <xsl:variable name="vInDir" select=
    "self::*[direction = 'in']"/>
  <rule type="{action}">

    <src>
      <xsl:apply-templates select=
        "remote[$vInDir] | local[not($vInDir)]"/>
    </src>
    <dst>
      <xsl:apply-templates select=
       "local[$vInDir] | remote[not($vInDir)]"/>
    </dst>
  </rule>
</xsl:template>

<xsl:template match="local | remote">
  <xsl:value-of select="."/>
</xsl:template>
</xsl:stylesheet>

<policy-rules>
<fw-rule-order>
   fwrule3
   fwrule1
   fwrule2
</fw-rule-order>
<fw-rules>
   <rule name="fwrule1">
      <direction>out</direction>
      <action>pass</action>
      <remote>192.168.129.31</remote>
      <local>192.168.129.67</local>
   </rule>
   <rule name="fwrule2">
      <direction>in</direction>
      <action>drop</action>
      <remote>192.168.129.32</remote>
      <local>192.168.129.67</local>
   </rule>
   <rule name="fwrule3">
      <direction>out</direction>
      <action>pass</action>
      <remote>192.168.129.33</remote>
      <local>192.168.129.67</local>
   </rule>
</fw-rules>
</policy-rules>

<policy>
<rule type="pass">
  <src>192.168.129.67</src>
  <dst>192.168.129.33</dst>
</rule>
<rule type="pass">
  <src>192.168.129.67</src>
  <dst>192.168.129.31</dst>
</rule>
<rule type="drop">
  <src>192.168.129.32</src>
  <dst>192.168.129.67</dst>
</rule>
</policy>

--
Cheers,
Dimitre Novatchev
---------------------------------------
Truly great madness cannot be achieved without significant intelligence.
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To invent, you need a good imagination and a pile of junk
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You've achieved success in your field when you don't know whether what
you're doing is work or play