Why won't xpath pickup a node when there is attribute data present?

Question

Can anyone explain to me why the following xslt:

<xsl:if test="EventDocument">

Does not pickup this xml tag?

<EventDocument xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.itron.com/ItronInternalXsd/1.0/">

it works when I delete the attributes from the tag, which makes no sense to me.

I.E. the above test passes when i modify the input to be:

<EventDocument>

I'm using xslt 2.0 (saxon parser) Thanks in advance

score 2 · Accepted Answer · edited May 23 '17 at 12:27

xmlns is "reserved attribute" - it is definition of mapping of namespace prefix to full node namespace. Covered in details in What does "xmlns" in XML mean?

I.e. actual name of the node in your case is "http://www.itron.com/ItronInternalXsd/1.0/" EventDocument, but you trying to select "" EventDocument (Node with name "EventDocument" and empty namespace).

Depending on your XPath engine you need either

pass mapping of your namespace prefixes to namespaces
use explicit matching to namespace and node names. *[namespace-uri()="http://www.itron.com/ItronInternalXsd/1.0/" and local-name()=="EventDocument"]
cheat and just match node names *[local-name()=="EventDocument"]

(local-name and namespace-uri covered in http://www.w3.org/TR/xpath/#section-Node-Set-Functions).

@JLRishe, you are absolutely right - should be `local-name`, not `node-name`. — Alexei Levenkov, Jan 17 '13 at 17:17

Ian Roberts · Answer 2 · 2013-01-17T17:23:56.263

By default, unprefixed element names in XPath expressions refer to elements with no namespace, thus an expression EventDocument selects elements with local name "EventDocument" and no namespace. The

<EventDocument ... xmlns="http://www.itron.com/ItronInternalXsd/1.0/">

element does not match this pattern, as it is in the http://www.itron.com/ItronInternalXsd/1.0/ namespace.

You have two choices, either

bind that namespace to a prefix in the stylesheet, then use the prefix in the XPath expression, or
(since you say you are in XSLT 2.0) use xpath-default-namespace

Example of 1

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
       xmlns:itron="http://www.itron.com/ItronInternalXsd/1.0/"
       version="2.0">

  <xsl:template match="itron:example">
    <xsl:if test="itron:EventDocument">....</xsl:if>
  </xsl:template>
</xsl:stylesheet>

Example of 2

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
       xpath-default-namespace="http://www.itron.com/ItronInternalXsd/1.0/"
       version="2.0">

  <xsl:template match="example">
    <xsl:if test="EventDocument">....</xsl:if>
  </xsl:template>
</xsl:stylesheet>

My personal preference is for option 1, on the "principle of least surprise" basis for anyone who has to maintain the stylesheet in future (including the original author, coming back to the code after a few months break...).

Why won't xpath pickup a node when there is attribute data present?

2 Answers2