Question

I’m learning XSLT. These questions may be obvious, but I’m really stuck now.
Oxygen returns the following two kind of errors:

1. Namespace is not declared for ‘ownFunction()’. (“undeclared namespace prefix {xs}”)

2. unknown system function index-of-string()

   The XSLT function index-of-string I got from this website doesn’t seems to be recognized

This is a simplified version of the XSL file:

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0"     xmlns:foo="http://www.wathever.com">
<xsl:output method="xml" />

  <xsl:function name="foo:ownFunction" as="xs:string">
    <xsl:param name="string" as="xs:string"/>

        <xsl:choose>

          <xsl:when test='contains($string,"src=")'>
            <xsl:variable name="position"><xsl:value-of select="index-of-string($string,'src=')"/>+<xsl:number value="10"/></xsl:variable>
            <xsl:variable name="partString"><xsl:value-of select="substring($string,$position)"/></xsl:variable>
            <xsl:variable name="length"><xsl:value-of select="index-of-string($partString,'quot;')"/> - <xsl:number value="2"/></xsl:variable>
            <xsl:value-of select="substring($partString,1,$length)"/>
          </xsl:when>

          <xsl:otherwise>
            <xsl:value-of select="hotpot-jmatch-file/data/title"/>
          </xsl:otherwise>

        </xsl:choose>
  </xsl:function>

  <xsl:template match="/">
    <data>
      <title>
        <xsl:variable name="string"><xsl:value-of select="hotpot-jmatch-file/data/title"/></xsl:variable>
        <xsl:value-of select="foo:ownFunction($string)"/>
      </title>
    </data>
  </xsl:template>
</xsl:stylesheet>

Answer 1

Oxygen returns the following two kind
of errors:

1) Namespace is not declared for
‘ownFunction()’. (“undeclared
namespace prefix {xs}”)

This is actually an XML issue. Any XSLT stylesheet myst be a well-formed XML document. Among other requirements for well-formedness, any namespace prefix used must be bound to a namespace URI in a namespace declaration.

To correct this bind the "xs" prefix to "http://www.w3.org/2001/XMLSchema" — this means to add xmlns:xs="http://www.w3.org/2001/XMLSchema" to an element (usually the top element is a good choice for this namespace.

You have the same problem with "foo:ownFunction". You must have the prefix "foo" bound/defined and visible, before using it. Just add xmlns:foo="my:foo" to the top element of your stylesheet.

2) “unknown system function
index-of-string()”. The XSLT function
“index-of-string” I got from this
website doesn’t seems to be
recognized:
http://www.xsltfunctions.com/xsl/functx_index-of-string.html

You have forgotten to either copy and paste the function from Priscilla Walmsley’s site or to save it in a separate file (recommended) and then use <xsl:import> or <xsl:include> to import/include this stylesheet file to your transformation.

Finally, such issues show that you need a more systematic introduction of XSLT. Get a good book and read it well. You won’t be sorry. This answer may be useful in listing what I consider good XSLT and XPath learning resources.