- From: <john.nj.davies@bt.com>
- Date: Thu, 21 Nov 2002 11:02:26 -0000
- To: sandro@w3.org, danny666@virgilio.it
- Cc: www-rdf-interest@w3.org, tarod@SoftHome.net
A good introduction to the issues of truth , self-reference and reification can be found in Ray Turner's "Truth and Modality for Knowledge Representation" book. Dr John Davies Manager, Advanced Business Applications BTexact Technologies Adastral Park Ipswich IP5 3RE UK e: john.nj.davies@bt.com w: www.exago.com t: +44 1473 609583 f: +44 1473 609832 BTexact Technologies is a trademark of British Telecommunications plc Registered office: 81 Newgate Street London EC1A 7AJ Registered in England no. 1800000 This electronic message contains information from British Telecommunications plc which may be privileged or confidential. The information is intended to be for the use of the individual(s) or entity named above. If you are not the intended recipient be aware that any disclosure, copying, distribution or use of the contents of this information is prohibited. If you have received this electronic message in error, please notify us by telephone or email (to the numbers or address above) immediately. -----Original Message----- From: Sandro Hawke [mailto:sandro@w3.org] Sent: 21 November 2002 10:23 To: Danny Ayers Cc: www-rdf-interest@w3.org; tarod@SoftHome.net Subject: Re: Contexts? (again) > so as far as I can see can only be done in the RDF model something like > > m3{ > {S1} -isFrom-> m1 > {S2} -isFrom-> m1 > ... > {S1} -isFrom-> m2 > {S2} -isFrom-> m2 > } > > which not only is convoluted & long-winded but also involves the dread > reification. > > Suggestions? Don't dread reification. It's just quoting-after-parsing, which is logically equivalent to quoting. Ever try to write a computer program that didn't use strings? Heck, putting programs and data in the same kind of place is the essense of the Von Neumann architecture which basically all computers use! That doesn't mean you have to write programs that modify their own object code, especially not the code for the routine which is currently running! RDF certainly has the danger of self-reference loops, but until you introduce a truth predicate, you're okay, and there's been a lot of work since Kripke to suggest we can have safe truth predicates with semantics which match our intuitions. I expect most applications will handle de-reification in application code, so they probably don't need a formal solution to this. My current suggested truth predicate is WellFormedAndTrue, where being well-formed includes being able to be re-written in a truth-preserving manner to a form without negated self-references; this is (as far as I can tell) what KIF3 had, before they took it out as being unnecessary for the intended apps. My current reading material is "The Liar: An Essay on Truth and Circularity" by Jon Barwise and John Etchemendy. It starts with a bit of a rebuke to logicians who throw the baby out with the bathwater on this subject. I haven't gotten far enough to understand what different kind of truth predicate they might suggest. (BTW, I think the proper name for this kind of {...} construct is "formula literals." They may function as a kind of context, but syntactically they denote logical formulas (which are RDF graphs here) very much like "..." constructs denote text strings and [0-9]* constructs denote numbers.) -- sandro
Received on Thursday, 21 November 2002 07:44:22 UTC