this script converts an instance path to an RNG path

Another XSLT code snippet for anyone using RNG out there. Here's a 
snippet to convert an instance document path into an XPath-like string 
that will locate the correct segment of a Relax NG (RNG) grammar.
The input param "fragment" might be something like 
"/resume/header/contact and then output will be something like 
"//*[(_at_)name='resume']//*[(_at_)name='header']//*[(_at_)name='contact']/*". You 
would then call dyn:evaluate() in EXSLT (or whatever equivalent you 
have) on the resulting string to turn it into a genuine XPath.
Comments welcome as always.

  <!-- Converts an instance path to an RNG path -->
  <xsl:template name="inst2rngPath">
    <xsl:param name="fragment"/>
    <xsl:choose>
      <xsl:when test="starts-with($fragment, '/')">  <!-- strip 
beginning / -->
        <xsl:call-template name="inst2rngPath">
          <xsl:with-param name="fragment" 
select="substring-after($fragment, '/')"/>
        </xsl:call-template>
      </xsl:when><xsl:otherwise>
        <xsl:text>//*[(_at_)name='</xsl:text>
        <xsl:choose><xsl:when test="substring-before($fragment, '/')">
            <xsl:value-of select="substring-before($fragment, '/')"/>
          </xsl:when><xsl:otherwise>
            <xsl:value-of select="$fragment"/>
        </xsl:otherwise></xsl:choose>
        <xsl:text>']</xsl:text>
        <xsl:choose>
          <xsl:when test="contains($fragment, '/')">  <!-- recursive 
step -->
            <xsl:call-template name="inst2rngPath">
              <xsl:with-param name="fragment" 
select="substring-after($fragment, '/')"/>
            </xsl:call-template>
          </xsl:when><xsl:otherwise>  <!-- default step -->
            <xsl:text>/*</xsl:text>
          </xsl:otherwise>
        </xsl:choose>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

simon
--
www.simonwoodside.com -- 99% Devil, 1% Angel


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