Path: text.usenetserver.com!out03b.usenetserver.com!news.usenetserver.com!in02.usenetserver.com!news.usenetserver.com!postnews.google.com!news1.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local02.nntp.dca.giganews.com!nntp.pipex.net!news.pipex.net.POSTED!not-for-mail NNTP-Posting-Date: Mon, 03 Mar 2008 11:24:20 -0600 Reply-To: "Roy Hann" From: "Roy Hann" Newsgroups: comp.databases.theory,comp.object References: <0cd61579-0f26-422c-9aec-908ffdea59ff@i7g2000prf.googlegroups.com> <7vqdnf21dLOnrVHanZ2dnUVZ_tuonZ2d@wideopenwest.com> Subject: Re: Object-relational impedence Date: Mon, 3 Mar 2008 17:24:20 -0000 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.2180 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Message-ID: Lines: 30 X-Usenet-Provider: http://www.giganews.com NNTP-Posting-Host: 82.133.118.245 X-Trace: sv3-2JbdY279LF2FGxROmZ8qCrf2I63DoK1lpeRfFKLgvivuela4ftOkzLCA+1fbwbSTo9PavjMl7TaOi2D!QFF+KMLLVeBPH2gruayIcETMbbuXn56WLCC9qfROVnZr3rhaFDw1TXKRZO2KUwSAwp/j23j26Ya8!AAkZfmyNOHO5W+Tr9BFA X-Complaints-To: abuse@dsl.pipex.net X-DMCA-Complaints-To: abuse@dsl.pipex.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.37 Xref: usenetserver.com comp.databases.theory:170226 comp.object:264393 X-Received-Date: Mon, 03 Mar 2008 12:24:21 EST (text.usenetserver.com) "Thomas Gagne" wrote in message news:7vqdnf21dLOnrVHanZ2dnUVZ_tuonZ2d@wideopenwest.com... > JOG wrote: >> I wondered if we might be able to come up with some agreement on what >> object-relational impedence mismatch actually means. I always thought >> the mismatch was centred on the issue that a single object != single >> tuple, but it appears there may be more to it than that. >> > The issue as I've discovered it has to do with the fact OO systems are > composed of graphs of data and RDBs are two-dimensional. RDBs are not two-dimensional, they are n-dimensional. You are confusing the picture of the thing with the thing. I have a three dimensional kitchen table. I have an RDB table with three columns (dimensions) called length, width and height that describes it. > What defines an account in an RDB may be composed of multiple tables. > An RDB might express multiple account types through multiple tables > where OO may reflect it as multiple classes. Attempts to make RDBs > function as graphs through mapping tools results in disappointing > performance and, in my experience, too much mapping, too much > infrastructure, and too much language/paradigm-specific layers. In > short, way more code, way more maintenance, and way more job-security > for consultants, pundits, and tool providers. I completely, 100% agree with that. Code is evil. Roy