[Bug 8791] [XPath21] Allowing intermediate XPath steps to return atomic values

http://www.w3.org/Bugs/Public/show_bug.cgi?id=8791


Michael Kay <mike@saxonica.com> changed:

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                 CC|                            |mike@saxonica.com




--- Comment #1 from Michael Kay <mike@saxonica.com>  2010-01-21 23:02:40 ---
There's a long history to this one.

There were many attempts during the development of XPath 2.0 to persuade the WG
of the need for a "simple mapping operator" that would allow any expression on
the left and any expression on the right. Some advocated using "/" as this
operator, but there were two objections: it would mean that 1/2 evaluates to 2;
and it wouldn't work for nodes, because the current path operator is not a
simple mapping, because it eliminates duplicates and sorts into document order.
So others advocated a different operator; but none was found that everyone
liked (and some people didn't see the need anyway).

Then at a very late stage of development an IBM reviewer proposed overloading
"/" to allow the rhs to select atomic values, and this was accepted.

Allowing the lhs to select atomic values as well is in some ways a logical
development. It still leaves the problem of (1/2), and it also leaves the
problem of deciding under exactly what circumstances the sorting and
deduplication should occur. The case where the lhs selects atomic values and
the rhs selects nodes is probably unusual, but it can't be ignored.


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Received on Thursday, 21 January 2010 23:02:42 UTC