When is a node not itself?

I've been discussing the collation of nodes from different
documents with (one of?) the author(s) of Sablotron, which
doesn't address this issue properly yet. (If you're reading
this Tom, I hope you don't mind me raising this here)

He raised the following question:
 
 Consider the following 3 files. The
 input file for the genid-question.xsl stylesheet is irrelevant.
 
 <!-- genid-question.xsl -->
 <xsl:transform xmlns:xsl='http://www.w3.org/1999/XSL/Transform'    
 version='1.0'>
 <xsl:template match='/'>
 <xsl:value-of select="generate-id(document('genid1.xml')/a/b) =
     generate-id(document('genid2.xml')/b)"/>
 </xsl:template>
 </xsl:transform>
 
 <!-- genid1.xml -->
 <!DOCTYPE a [ <!ENTITY genid2 SYSTEM "genid2.xml"> ]>
 <a> &genid2; </a>
 
 <!-- genid2.xml -->
 <b/>
 
 Shouldn't this output true? I think it should, but neither XT nor Saxon
 do.

The spec doesn't seem to address this question explicitly.
Does anybody have an answer?

 .robin.
 
-- 
A man, a plan, a cat, a ham, a yak, a yam, a hat, a canal--Panama!


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