Path: newssvr20.news.prodigy.com!newsmst01a.news.prodigy.com!prodigy.com!news-FFM2.ecrc.net!kibo.news.demon.net!news.demon.co.uk!demon!thewolery.demon.co.uk!wol From: "Anthony W. Youngman" Newsgroups: comp.databases.theory Subject: Re: godel-like incompleteness of relational model Date: Thu, 20 May 2004 22:39:48 +0100 Organization: vinny-puch Lines: 43 Message-ID: References: <3Nrpc.40241$TT.30435@news-server.bigpond.net.au> <40a75492.1033926@news.wanadoo.es> <40aa006f.9003316@news.wanadoo.es> <40ab3fd9.4132902@news.wanadoo.es> <6%_qc.6458$NK4.656343@stones.force9.net> Reply-To: "Anthony W. Youngman" NNTP-Posting-Host: thewolery.demon.co.uk Mime-Version: 1.0 Content-Type: text/plain;charset=us-ascii;format=flowed X-Trace: news.demon.co.uk 1085089365 13348 158.152.222.21 (20 May 2004 21:42:45 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Thu, 20 May 2004 21:42:45 +0000 (UTC) User-Agent: Turnpike/6.02-U () Xref: newssvr20.news.prodigy.com comp.databases.theory:26946 In message <6%_qc.6458$NK4.656343@stones.force9.net>, Paul writes >mountain man wrote: >>>>>And what is the problem with The Relational Model? >>>> >>>>It has a Godel-like incompleteness: >> >>http://www.mountainman.com.au/software/history/relational_model_incompl >>ete.htm > >I don't quite understand what you mean here. Even if you think that >relational theory is missing something, I don't think it is a >"Godel-like" incompleteness. > >>>I'm no mathematician, but didn't Godel prove that 'any' formal system >>>is incomplete? >> Yes, he did. But I am being specific about provision of one >>specific >> instance in which the incompleness of the RM is comprehendable. > >Well, Godel acually proved that first-order predicate logic (upon which >the relational model is based) is complete in some sense. The >Incompleteness theorem only applies to theories that are above a >certain complexity. To add to the confusion, there are slightly >different meanings of "complete" here. See this page for more details: >http://www.sm.luth.se/~torkel/eget/godel/completeness.html And isn't there something about if they are complete, then they also have to be simplistic (and therefore cannot be real-world accurate)? > >I think essentially the difference is that you need to use logic to >show that some other theories are incomplete, but to show the >completeness of logic itself you've got a bit of a self-referential >paradox. I could be completely wrong here though. Very interesting though. > Cheers, Wol -- Anthony W. Youngman - wol at thewolery dot demon dot co dot uk HEX wondered how much he should tell the Wizards. He felt it would not be a good idea to burden them with too much input. Hex always thought of his reports as Lies-to-People. The Science of Discworld : (c) Terry Pratchett 1999