From: Christian de Sainte Marie <csma@ilog.fr>

Date: Tue, 15 Jan 2008 16:45:36 +0100

Message-ID: <478CD520.2080309@ilog.fr>

To: Michael Kifer <kifer@cs.sunysb.edu>

CC: RIF WG <public-rif-wg@w3.org>

Date: Tue, 15 Jan 2008 16:45:36 +0100

Message-ID: <478CD520.2080309@ilog.fr>

To: Michael Kifer <kifer@cs.sunysb.edu>

CC: RIF WG <public-rif-wg@w3.org>

Michael Kifer wrote: >> >>What if the new truth value E was such that: >> ~E = E/\F = E/\T = E\/F = E\/T >> = E :- T = E :- F = T :- E = F :- E >> = Forall E = Exists E >> = E >>so that as soon as you have an E somewhere, everything becomes E (so, >>the intuitive semantics of E is more like "undefined" than "error")? > > This is not a truth table for undefined (U). With the U value, U/\F=F and > U\/T=T. In any case, it is not very clear what the truth table should > really be. In my proposal the only diff with yours was E\/T=T, but I think > I made a typo there (do not remember what I was thinking). No, apparently, what you were thinking is to use a thruth table for undefined: > b. This option introduces a new truth value, called E (error) such that > ~E = E, E/\F=F, E/\T=E, E\/F=E, E\/T=T. Then we can say that > p(a,b,c,...) has truth value E if at least of of the args is _|_. So, we might call option (b) the "undefined" option, and the one corresponding to the truth table where everything that touches E becomes E: the "error" option. > So, I consider this a risky path given our time constraints. But we must consider it to make an informed decision, right? >>>Comments? (esp. if anyone can see whether option (a) breaks somewhere) > > It is not easy to "see" something like that. One needs to check, which is > very time consuming. My crystal ball says that the chances of breakage are > over 50%. Replying to yourself? :-) ChristianReceived on Tuesday, 15 January 2008 15:45:47 GMT

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