[XQuery] A.2.2 Lexical Rules: bad transitions

• From: Michael Dyck <jmdyck@ibiblio.org>
• Date: Fri, 23 Jan 2004 01:07:18 -0800
• To: public-qt-comments@w3.org
• Message-id: <4010E446.524516B8@ibiblio.org>

XQuery 1.0: An XML Query Language
W3C Working Draft 12 November 2003
A.2.2 Lexical Rules
Some of the lexical states have incorrect transitions, causing the lexer
to reject valid queries.
Specifically:
------------------------------------------------------------------------
Query:   <!---- blah ----> | e
Query:   <?PITarget ?> | e
Query:   <![CDATA[x]]> | e
Problem: In each case, after the ">", the lexer is in DEFAULT, which
         doesn't recognize "|" (or any other operator).
Fix:     In DEFAULT, for the transitions on "<!----", "<?", and
         "<![CDATA[", change "pushState()" to "pushState(OPERATOR)".
Note: I reported this on November 28, 2002 (three versions ago), in
https://lists.w3.org/Archives/Public/public-qt-comments/2002Nov/0105.html
------------------------------------------------------------------------
Query:   <Q> { typeswitch (e) case e return e default return e } </Q>
Problem: After the "}", the lexer is in OPERATOR, which doesn't
         recognize "</".
Fix:     In DEFAULT, the transition for <"typeswitch" "("> should not
         involve "pushState(OPERATOR)".
------------------------------------------------------------------------
Query:   processing-instruction {x} {x}
Problem: Accepting the last "}" causes popState() on an empty stack.
Fix:     In OPERATOR, the transition for "{" needs "pushState()".
------------------------------------------------------------------------
Query:   declare variable $x as processing-instruction()? external; e
Problem: After the ")", the lexer is in OPERATOR, which doesn't
         recognize "?".
Fix:     In ITEMTYPE, the transition for <"processing-instruction" "(">
         should change "pushState(OPERATOR)" to
         "pushState(OCCURRENCEINDICATOR)".
------------------------------------------------------------------------
Query:   declare variable $x  external; e
Query:   declare function Q() external; e
Problem: These leave DEFAULT on the stack. It's not clear whether this
         means that the lexer should reject them, but even if not, it's
         still bad form: a lexer with a maximum stack size would be much
         more likely to hit its limit.
Fix:     In DEFAULT, for the transitions on <"declare" "variable" "$">
         and <"declare" "function">, don't "pushState(DEFAULT)".
------------------------------------------------------------------------
-Michael Dyck

Received on Friday, 23 January 2004 04:14:26 UTC