Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!drn.maxwell.syr.edu!news.maxwell.syr.edu!postnews.google.com!f14g2000cwb.googlegroups.com!not-for-mail From: "vc" Newsgroups: comp.databases.theory Subject: Re: So what's null then if it's not nothing? Date: 22 Dec 2005 12:52:31 -0800 Organization: http://groups.google.com Lines: 22 Message-ID: <1135284751.736656.196220@f14g2000cwb.googlegroups.com> References: <1134354197.583597.21280@o13g2000cwo.googlegroups.com> <5fm3q11edj412gbk98h39sjagb8ksurtj0@4ax.com> <4eqjq11u90jb81gon89nlfaq6elid3n4ik@4ax.com> NNTP-Posting-Host: 65.244.78.22 Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" X-Trace: posting.google.com 1135284756 17380 127.0.0.1 (22 Dec 2005 20:52:36 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Thu, 22 Dec 2005 20:52:36 +0000 (UTC) In-Reply-To: <4eqjq11u90jb81gon89nlfaq6elid3n4ik@4ax.com> User-Agent: G2/0.2 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 2.0.50727),gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: f14g2000cwb.googlegroups.com; posting-host=65.244.78.22; posting-account=thIdtgwAAAAhUVpIR1L4IFjCXWRKlxtG Xref: dp-news.maxwell.syr.edu comp.databases.theory:35292 Hugo Kornelis wrote: [...] > And NULL should always propagate > in logic - i.e. expr1 log-oper expr2 should always result in NULL if > either expr1 or expr2 is NULL, regardless of the value of the other > expression and regardless of the logical operator. Then you have a four-valued logical mongrel half-Kleene's (or Lukasiewicz's) and half-Bochvar's which you intend to use in an ad hoc fashion without clearly understanding what each truth value {true, false, unknown, meaningless (aka NULL) } is supposed to model. I am not sure if anyone can find a system like that very useful.. > > Or, to make a long story a lot shorter: I disagree with Codd's views aas > outline in this paper. > > Best, Hugo > -- > > (Remove _NO_ and _SPAM_ to get my e-mail address)