Path: news.cambrium.nl!textnews.cambrium.nl!feeder3.cambrium.nl!feed.tweaknews.nl!postnews.google.com!35g2000pry.googlegroups.com!not-for-mail From: vadimtro@gmail.com Newsgroups: comp.databases.theory Subject: Re: Onto a potential relational manipulation language Date: Fri, 12 Dec 2008 12:49:18 -0800 (PST) Organization: http://groups.google.com Lines: 26 Message-ID: References: <63a4d28c-948c-491a-a27e-c5a1496b85d5@z28g2000prd.googlegroups.com> <934bce99-fe7d-43a0-8678-4d7934ab6fc3@a26g2000prf.googlegroups.com> <3ebb61cf-641f-4bb8-9d13-8561ea27b8c1@r37g2000prr.googlegroups.com> NNTP-Posting-Host: 148.87.1.167 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1229114959 19689 127.0.0.1 (12 Dec 2008 20:49:19 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Fri, 12 Dec 2008 20:49:19 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: 35g2000pry.googlegroups.com; posting-host=148.87.1.167; posting-account=dmGV1QoAAAD_iLea43F098rb5Yhuc0yg User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4,gzip(gfe),gzip(gfe) Xref: news.cambrium.nl On Dec 12, 11:58=A0am, paul c wrote: > Regarding quantification, I thought Codd's algebra > included analogies for Exists and Forall in the projection (fundamental, > can't be defined in terms of the other fundamental ops, ie., REMOVE, > NAND or NOR, and TCLOSE) and division (defineable in terms of the other > ops). =A0Same must be so of D&D A-algebra. =A0If so, RL must at least hav= e > quantification since it has a form of projection in its lattice union. What I was saying that algebraic version of predicate calculus (whatever this might be) doesn't have *explicit* quantifiers. By explicit I mean their syntactic appearance, especially the introduction of auxiliary bind variables. Arguably quantifiers with these bind variables introduce a steep learning curve for anybody who transitioned from propositional to predicate calculus. > ... such as the > "multi-relations" Darwen has written about lately (note I'm not saying > that he advocates them just because he's written about them), where > tuples in the same structure can have different attributes... Missing information...yawn. Seriously, I find RL system operating with classic relations be challenging enough, at least I'm not ready to expand the scope yet. From the axiomatic perspective it is interesting what other structures (other than relations) fit into RL axiom system...