Hi Folks,
This XML document has id-idref references that create a circular dependency:
<document>
<item id="HF">
<title>Huckleberry Finn</title>
<for-more-info idref="MT"/>
</item>
<item id="MT">
<name>Mark Twain</name>
<for-more-info idref="HF"/>
</item>
</document>
I want an XPath expression which returns true if there is an <item> element
that contains a <for-more-info> element with an idref reference that ultimately
loops back around to the <item> element. For the above XML document, the XPath
expression should return true. Here's an XPath expression that seems to work as
desired:
for $i in /document/item return
for $j in $i/for-more-info return
for $k in /document/item[@id eq $j/@idref] return
if ($k/for-more-info/@idref eq $i/@id) then true() else ()
That XPath expression works fine when the cycle is between two <item> elements
but it doesn't work when the cycle is between three or more <item> elements. Is
there a way to write an XPath 2.0 expression to detect a cycle, regardless of
how big the cycle is? /Roger
This XML has a cycle between three <item> elements:
<document>
<item id="HF">
<title>Huckleberry Finn</title>
<for-more-info idref="MT"/>
</item>
<item id="MT">
<name>Mark Twain</name>
<for-more-info idref="SP"/>
</item>
<item id="SP">
<publisher>Springer</publisher>
<for-more-info idref="HF"/>
</item>
</document>
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