evaluating the following-sibling axis

Hi,

Maybe it's not the right place for this question, but no one in comp.text.xml could/would provide an answer.

I've a certain lack of understanding the semantics of the
following-sibling axis. Well not in the sense of what it returns. More in terms of evaluating it properly when interpreting a XQuery expression by means of software.

Suppose this document:

<a>
  <b/>
  <c/>
  <d/>
</a>

and the expression:

/a/b/following-sibling::*

according to XPath 2.0 section 3.2.1.1 the element nodes for c and d
are the result of the expression.

So far so good. But to compute the result I'd use the XQuery 1.0 and
XPath 2.0 Formal Semantics paper section 4.2.1.1. There an expression
for evaluating the following-sibling axis is given:

[following-sibling:: NodeTest]Axis 
== 
[let $e := . in parent::node()/child:: NodeTest [.<<$e]]Expr 

and that is the problem.

How do I evaluate the left side of the equation?
let $e := . in parent::node()/child::* [.<<$e]

In my understanding parent::node()/child::* would describe the
sequence (b,c,d)
But the predicate has to be considered too. What is the context item
expression in the predicate is refering to? What values/nodes will $e
hold?
What is the context item expression left of "in" is refering to? And
what would be the exact value of $e at the end of the evaluation? Will
it just be the sequence of the two element nodes "c" and "d"?

Thanks for help & Cheers,
Daniel

Received on Monday, 22 March 2004 07:05:33 UTC