Path: text.usenetserver.com!out03b.usenetserver.com!news.usenetserver.com!in01.usenetserver.com!news.usenetserver.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.de!t-online.de!newsfeed.freenet.de!multikabel.net!feed20.multikabel.net!sn-xt-ams-06!sn-xt-ams-04!sn-ams!sn-feed-ams-01!sn-post-ams-01!sn-post-ams-02!sn-post-sjc-01!supernews.com!corp.supernews.com!not-for-mail From: Jonathan Leffler Newsgroups: comp.databases.theory Subject: Re: RM and abstract syntax trees Date: Wed, 31 Oct 2007 21:31:32 -0700 Organization: Randomly Disorganized Message-ID: <13iill2q6gusd6c@corp.supernews.com> User-Agent: Thunderbird 2.0.0.5 (Macintosh/20070716) MIME-Version: 1.0 References: <1193713604.283167.146850@e34g2000pro.googlegroups.com> <1193743772.498246.198100@e34g2000pro.googlegroups.com> <1193790888.643295.55060@e34g2000pro.googlegroups.com> <1193796029.446713.108270@k35g2000prh.googlegroups.com> <1193810534.716595.45040@t8g2000prg.googlegroups.com> <1193887763.783354.250150@k35g2000prh.googlegroups.com> In-Reply-To: <1193887763.783354.250150@k35g2000prh.googlegroups.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@supernews.com Lines: 33 Bytes: 2959 Xref: usenetserver.com comp.databases.theory:167132 X-Received-Date: Wed, 31 Oct 2007 23:31:32 EST (text.usenetserver.com) Marshall wrote: > On Oct 31, 7:50 pm, David BL wrote: >> Isn't it helpful to see the analogy with a pointer dereference? >> >> I'll leave it up to you as to whether you dislike the analogy between >> node identifiers and pointer values, and the idea that a join can be >> compared to a pointer dereference. Perhaps you are right and the >> analogy creates confusion. > > I think if we are clear about it being an analogy we are on solid > ground. But as soon as we start thinking pointers and references > are the *same* thing we are in trouble, because now we can't > see the differences anymore. > > I think Date actually nails this issue. He says (roughly) that > pointers add complexity but don't add any expressive power. Isn't the other 'point' that 'pointers point somewhere' but values stored in a relation don't - that relational database bases work on associative addressing. In particular, even in a foreign key, the value doesn't point to the referenced primary key; it merely contains the same value as some entry in the referenced table. It may also contain the same value as a large number of other places in the database. -- Jonathan Leffler #include Email: jleffler@earthlink.net, jleffler@us.ibm.com Guardian of DBD::Informix v2007.0914 -- http://dbi.perl.org/ publictimestamp.org/ptb/PTB-1677 whirlpool 2007-11-01 03:00:04 136EC3850C6A351ABA4F75728C29638E5FD3A94DFC10470DA9FC9E7EC2E70EA48251A6 CEFD27B053762ABE7BC69C403990C43628769C2162BA5FAB540097F23