Path: newssvr20.news.prodigy.com!newsmst01a.news.prodigy.com!prodigy.com!prodigy.com!news.glorb.com!newsgate.cistron.nl!transit.news.xs4all.nl!not-for-mail Date: Wed, 05 May 2004 10:16:51 +0200 From: mAsterdam User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: nl, de, fr, en, en-us, ja, ko, zh MIME-Version: 1.0 Newsgroups: comp.databases.theory Subject: Re: Peter Chen and Charles Bachman References: <47mdnZBQ75-ZygXdRVn-jw@comcast.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Lines: 25 Message-ID: <4098a301$0$21804$e4fe514c@news.xs4all.nl> NNTP-Posting-Date: 05 May 2004 10:17:05 CEST NNTP-Posting-Host: 194.109.233.75 X-Trace: 1083745025 news.xs4all.nl 21804 [::ffff:194.109.233.75]:1851 X-Complaints-To: abuse@xs4all.nl Xref: newssvr20.news.prodigy.com comp.databases.theory:26206 Leandro Guimarães Faria Corsetti Dutra wrote: > Em Tue, 04 May 2004 22:53:51 -0400, Laconic2 escreveu: > > >>A model highlights certain features >>of the thing modeled precisely because it omits some of the detail. > > So a model omits data itself, and the DBMS, and the physical model. Yes, yes and yes, as far as ER-models are concerned. However, naive use of them starts with higher expectations. Children who get to learn how to use city-maps have to learn how to use them. It's not immediately appearent which aspects from the map they can trust, and which ones they can't. Learning how to make use of ER-models goes the same way. Expectation management is important. > Otherwise, it's a draft. > > You can't make much of analogies with the physical world. Analogies make models useful for design, teaching and planning purposes. They don't need to be physical.