Re: Object-relational impedence
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 04 Mar 2008 10:20:07 -0400
Message-ID: <47cd5a9b$0$4065$9a566e8b_at_news.aliant.net>
>>Roy Hann wrote:
>>
>>>"Thomas Gagne" <tga..._at_wide-open-west.com> wrote in message
>>>news:7vqdnf21dLOnrVHanZ2dnUVZ_tuonZ2d_at_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.
>>
>>That is a remarkably uninformed and ill-conceived sentence. It's rather
>>like comparing boats and cars saying boats have hulls and cars are
>>pretty. Regardless of truth, the comparison is pointless on its face.
>>
>>One can represent any graph on two-dimensional media just as one can
>>represent any relation on two-dimensional media. In fact, since a graph
>>is merely a set of vertices and a set of directed edges and since one
>>can easily represent vertices and directed edges as tuples, one can
>>easily represent any graph using relations.
>>
>>The Great Debate was had about 3 decades ago and graphs lost.
Date: Tue, 04 Mar 2008 10:20:07 -0400
Message-ID: <47cd5a9b$0$4065$9a566e8b_at_news.aliant.net>
Jan Hidders wrote:
> On 4 mrt, 00:02, Bob Badour <bbad..._at_pei.sympatico.ca> wrote: >
>>Roy Hann wrote:
>>
>>>"Thomas Gagne" <tga..._at_wide-open-west.com> wrote in message
>>>news:7vqdnf21dLOnrVHanZ2dnUVZ_tuonZ2d_at_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.
>>
>>That is a remarkably uninformed and ill-conceived sentence. It's rather
>>like comparing boats and cars saying boats have hulls and cars are
>>pretty. Regardless of truth, the comparison is pointless on its face.
>>
>>One can represent any graph on two-dimensional media just as one can
>>represent any relation on two-dimensional media. In fact, since a graph
>>is merely a set of vertices and a set of directed edges and since one
>>can easily represent vertices and directed edges as tuples, one can
>>easily represent any graph using relations.
>>
>>The Great Debate was had about 3 decades ago and graphs lost.
> > I beg to differ. What lost was the idea that a close coupling is > required between how the data is stored and how it is accessed / > queried, i.e., that in that sense you cannot have data independence. > But such data independence can be just as well achieved with graph- > based data models. > > -- Jan Hidders
Well, I have yet to see it. Until I see any real evidence of a graph-based data model with physical data independence, we will just have to disagree. Received on Tue Mar 04 2008 - 15:20:07 CET