Re: Object-relational impedence
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 03 Mar 2008 18:24:03 -0400
Message-ID: <47cc7a87$0$4031$9a566e8b_at_news.aliant.net>
>
> Most of them are statements about philosophy or practice rather than
> absolutes; thus its hard for them to be objectively or "blatantly"
> wrong. Whether that's a good thing or not is another issue. I see the
> list as a starting point for discussion even if it does not settle
> everything.
>
> It brings up interesting questions, such as why not have schema
> inheritance? If inheritance is good or OO, why is it not good for
> relational schema's? The answer is that OO and relational approach
> things differently.
Date: Mon, 03 Mar 2008 18:24:03 -0400
Message-ID: <47cc7a87$0$4031$9a566e8b_at_news.aliant.net>
topmind wrote:
> On Mar 3, 10:54 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
>>topmind wrote: >> >>>JOG wrote: >> >>>>On Mar 3, 2:07 pm, Thomas Gagne <tga..._at_wide-open-west.com> wrote: >> >>>>>All attempts by applications to access a DB's tables and columns >>>>>directly violates design principles that guard against close-coupling. >>>>>This is a basic design tenet for OO. Violating it when jumping from OO >>>>>to RDB is, I think, the source of problem that are collectively and >>>>>popularly referred to as the object-relational impedance mismatch. >> >>>>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. >> >>>>I was hoping perhaps people might be able to offer perspectives on the >>>>issues that they have encountered. One thing I would like to avoid >>>>(outside of almost flames of course), is the notion that database >>>>technology is merely a persistence layer (do people still actually >>>>think that?) - I wonder if the 'mismatch' stems from such a >>>>perspective. >> >>>This came up in a nearby message. I borrowed the following text from >>>wikipedia: >> >>The text had too many blatant errors to start enumerating them all.
>
> Most of them are statements about philosophy or practice rather than
> absolutes; thus its hard for them to be objectively or "blatantly"
> wrong. Whether that's a good thing or not is another issue. I see the
> list as a starting point for discussion even if it does not settle
> everything.
>
> It brings up interesting questions, such as why not have schema
> inheritance? If inheritance is good or OO, why is it not good for
> relational schema's? The answer is that OO and relational approach
> things differently.
Your question presupposes that inheritance is good for OO. Received on Mon Mar 03 2008 - 23:24:03 CET