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XPath and XQuery: fn:xxx

Posted on 2015-01-21
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XPath and XQuery: fn:xxx

What exactly are the group of functions with a prefix of "fn:".

How are they different than something like format-number()

Is there a fn:xxx equivalent to format-number() ?

Thnkas
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Question by:Anthony Lucia
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Geert Bormans earned 500 total points
ID: 40563297
basically you will see the fn: used in books and web examples,
I never use them in my code
fn: indicates the namespace xmlns:fn="http://www.w3.org/2005/xpath-functions"
the namespace of the functions internaly defined in the XPath spec
but if you use the prefix, you also have to declare the prefix this way
xmlns:fn="http://www.w3.org/2005/xpath-functions"

eg.
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:fn="http://www.w3.org/2005/xpath-functions"
    exclude-result-prefixes="xs"
    version="2.0">
    <xsl:template match="/">
        <xsl:value-of select="fn:abs(5)"></xsl:value-of>
    </xsl:template>
</xsl:stylesheet>

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I simply use it without the prefix, for me that is much clearer
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    exclude-result-prefixes="xs"
    version="2.0">
    <xsl:template match="/">
        <xsl:value-of select="abs(5)"></xsl:value-of>
    </xsl:template>
</xsl:stylesheet>

Open in new window


You can not declare functions yourself in that namespace, so your own functions will always need to be prefixed
so the distinction is easy
(I think an early XPath recommendation draft had the fn: as mandatory for XPath functionsn but the requirement was dropped)

Anyhow, simply forget about fn:, they are the same
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