[Bug 2946] [XSLT] remove stability constraint in use-when

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2946

           Summary: [XSLT] remove stability constraint in use-when
           Product: XPath / XQuery / XSLT
           Version: Candidate Recommendation
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XSLT 2.0
        AssignedTo: mike@saxonica.com
        ReportedBy: joannet@ca.ibm.com
         QAContact: public-qt-comments@w3.org


According to the second table in section 3.12 (Conditional Element Inclusion), 
current datetime information and implicit timezone are available when 
evaluating a use-when expression.  Section 5.4.3 (Initializing the Dynamic 
Context) states that these two components must be stable.  To satisfy this 
stability constraint and to generate a current datetime value that is expected 
by the user, our implementation of the compiled processor cannot fully 
evaluate the use-when expression statically before byte-code generation.   We 
would like to avoid this because evaluating use-when during run-time adds 
complexity to our implementation.  An alternative without the added complexity 
and still satisfy the stability constraint is to fix the current datetime 
value to compile time, and other expressions accessing current datetime 
information would also return this value during run-time.  Unfortunately, our 
users would then always get a current-datetime value from the past.   In order 
to avoid the added complexity to our implementation and still provide the user 
with accurate datetime information in most cases,  I request for lifting the 
stability constraint for these two components only when used in a use-when 
expression.

Received on Monday, 27 February 2006 21:53:53 UTC