graph-traversal query

Im finding the dynamic assigning and traversing process in XSL quite confusing. Is there a logical way of traversing through a tree to determine the grandchild of an element albeit indirectly. So I know that my XML file is as below

-----------------------
<DEFCONCEPT id="10180" name="Car">
<PARENT>
<CONCEPT name="Automobile" ref="10181"/>
</PARENT>
<CHILD>
<CONCEPT name="Toyota" ref="10235"/>
</CHILD>
</DEFCONCEPT >
<DEFCONCEPT id="10235" name="Toyota">
<PARENT>
<CONCEPT name="Car" ref="10180"/>
</PARENT>
<CHILD>
<CONCEPT name="Corolla" ref="10279"/>
</CHILD>
</DEFCONCEPT >
<DEFCONCEPT id="10279" name="Corolla">
<PARENT>
<CONCEPT name="Toyota" ref="10235"/>
</PARENT>
</DEFCONCEPT >
-----------------------
and I want to reach the <DEFCONCEPT name="Corolla"> from the node <DEFCONCEPT name="Car"> because I have a query to determine the existence of a kind_of Car 'Corolla' irrespective of the case (upper or lower) in which it has been written and where in the hierarchy it exists. How will it be possible using XSLT?

Thanks
Rahil