- From: Tim Berners-Lee <timbl@w3.org>
- Date: Tue, 18 Oct 2005 09:31:09 -0400
- To: Eric Prud'hommeaux <eric@w3.org>
- Cc: public-rdf-dawg-comments@w3.org, Yosi Scharf <syosi@mit.edu>, Dan Connolly <connolly@w3.org>
Looks right to me. Thank you. Tim On Oct 18, 2005, at 8:59, Eric Prud'hommeaux wrote: > On Tue, Aug 02, 2005 at 11:27:24AM -0400, Tim Berners-Lee wrote: > >> >> The current last call draft states, >> >> "A value disjunction that encounters a type error on only one branch >> will return the result of evaluating the other branch." >> >> This seems to be a bug: inconsistent with the logic one would expect. >> It is inconsistent with the general rule that the disjunction of >> false with x is x for all x. The disjunction of false with a type >> error is therefore a type error. If not, the type error is masked. >> >> Example in english: An alarm should fire if either ?smokeDetected or >> the ?temperature is above 40. Suppose the ?smokeDetected is false >> and the temperature is (because of a bug) bound to something which >> can't be compared to 40 without a type error. The result should be >> that the alarm is a type error. Instead, with the wording above, the >> alarm is suppressed. >> >> Yosi Scharf found also that this rule for union means that de >> Morgan's laws don't hold properly, making the compilation and >> optimization of queries more difficult or impossible. >> > > Per the above text, and a hallway conversation with you, we've > re-arranged the truth table as follows: > > A B | A && B A || B > ---------------------- > E E | E E > E T | E T > E F | F E* > T E | E T > T T | T T > T F | F T > F E | F E* > F T | F T > F F | F F > > * changed to give priority to F || X => X > > This is specified with the words: > [[ > # Any expression other than logical or (||) or logical and (&&) that > encounters a type error will produce a type error. > # A logical or that encounters a type error on only one branch will > return will return TRUE if the other branch is TRUE and an error if > the other branch is FALSE. > # A logical and that encounters a type error on only one branch will > return will return an error if the other branch is TRUE and FALSE if > the other branch is FALSE. > # A logical or or logical and that encounters type errors on both > branches will produce a type error. > ]] > and clarified with the above truth table. > > If this text meets your requirements, please respond with [CLOSED] in > the subject to allow the issue tracking scripts to close this issue. > -- > -eric > > office: +81.466.49.1170 W3C, Keio Research Institute at SFC, > Shonan Fujisawa Campus, Keio University, > 5322 Endo, Fujisawa, Kanagawa 252-8520 > JAPAN > +1.617.258.5741 NE43-344, MIT, Cambridge, MA 02144 USA > cell: +81.90.6533.3882 > > (eric@w3.org) > Feel free to forward this message to any list for any purpose other > than > email address distribution. >
Received on Tuesday, 18 October 2005 13:31:21 UTC