Yes, "treat as" is there almost entirely for systems that do pessimistic
static type checking.

It can also, however, be used as an assertion mechanism, to document that
you expect a particular expression to return a particular type of value and
trigger a failure if it doesn't.

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

> -----Original Message-----
> From: Frans Englich [mailto:frans.englich@xxxxxxxxx] 
> Sent: 29 August 2005 22:07
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  Usage scenarios of 'treat as'
> 
> 
> Hi,
> 
> I'm curious on usage scenarios for the 'treat as' expression, 
> in particular 
> for when XSL-T 2.0 is the host language(if that matters).
> 
> In XPath 2.0 is verification of an operand's type(the 
> function conversion 
> rules) done at runtime(implementation dependent if guaranteed 
> runtime type 
> errors are detected statically), unless the implementation implements 
> "pessimistic" static type checking. (Right?)
> 
> In what case is the 'treat as' expression useful, or 
> required, when the 
> implementation does not do pessimistic, static type checking? 
> (that is, usage 
> scenarios which applies for all implementations regardless of 
> what optional 
> features that are implemented.)
> 
> From what I can tell, the 'treat as' expression is only 
> useful when writing 
> code that must work on implementations that implement 
> pessimistic type 
> checking.
> 
> Clarification, elaboration, & correction is appreciated.
> 
> 
> Cheers,
> 
> 		Frans