Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!drn.maxwell.syr.edu!news.maxwell.syr.edu!news.netins.net!not-for-mail From: "Dawn M. Wolthuis" Newsgroups: comp.databases.theory Subject: Re: Logical equivalence of simple and complex types under the relational model? Date: Mon, 29 Nov 2004 16:51:27 -0600 Organization: netINS InterNetNews site Lines: 26 Message-ID: References: NNTP-Posting-Host: 199.120.93.7 X-Trace: news.netins.net 1101768702 4566 199.120.93.7 (29 Nov 2004 22:51:42 GMT) X-Complaints-To: usenet@netins.net NNTP-Posting-Date: Mon, 29 Nov 2004 22:51:42 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Xref: dp-news.maxwell.syr.edu comp.databases.theory:28687 "Rene de Visser" wrote in message news:cofms4$vr$1@news.sap-ag.de... > I have read a number of papers that discuss whether complex data types > should be allowed under the relational model. > > What I haven't seen analysed is whether there is actually any logical > difference (upto renaming/isomorphism) between the resulting models. > > It seems to me at first sight that > > 1) RM with simple types > 2) RM with complex types > > are indistiguishable at the logical level. > If this is so why was there in the past debate about whether to allow > complex types or not, when it seems in theory (and in at least some > languages) it makes no logical difference? All data can be accounted for either way, but there is typically not a mapping between metadata. So, even if there is no logical difference, there is a semantic difference that is significant. --dawn