RE: [xml-dev] XML design of ((a and b) or c)

["Klotz, Leigh" <Leigh.Klotz@xerox.com>]

Yes, I think that's the same problem I pointed out.  We didn't see a way
to add if() other than as an extension function, and adding the ternary
operator semantics (conditional evaluation) as an XPath extension
function doesn't appear possible, and adding it outside the XPath
extension function mechanism would have made an incompatible XPath. 

On the nighmare issue, originally all XForms XPath extension functions
were in the XForms namespace, but we removed that as a result of public
comments that showed that the XPath 1.0 Recommendation did not allow
qualified names, and that neither XSLT nor XML Signature W3C
recommendations specified qualified names as extension functions.  

We contacted the XPath functions task force and got assurance that
extension functions would be namespaced in XPath 2.0.  But the botch is
with XPath 1.0 not allowing them.  (I realize that this flies in the
face of the extension function implementation of just about every XPath
implementation on the planet, but back in spec land, we had to be
compliant.)

Personally, I would welcome any helpful suggestions you have about
upward compatibility, with XForms 1.1 and with XPath 2.0.

Leigh.

-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com] 
Sent: Friday, December 15, 2006 3:24 PM
To: Klotz, Leigh; 'Rick Marshall'
Cc: 'Ken North'; xml-dev@lists.xml.org
Subject: RE: [xml-dev] XML design of ((a and b) or c)

> 
> XForms added one to its XPath functions, but it doesn't (and 
> can't) do conditional evaluation. 
> http://www.w3.org/TR/xforms/slice7.html#fn-if

Worse, the XForms if() function allows (and arguably requires) both the
"then" and "else" expressions to be evaluated regardless whether the
"condition" parameter is true or false.

(There's also a forwards compatibility nightmare looming because XForms
failed to put its "if" function in a private namespace: it now clashes
with
the XPath 2.0 "if" construct).

Michael Kay
http://www.saxonica.com/