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Re: model inherited object

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Wed, 21 Jun 2006 16:22:56 GMT
Message-ID: <Anemg.368$pu3.10948@ursa-nb00s0.nbnet.nb.ca>


deja_at_2bytes.co.uk wrote:

> sorry - crossposting (from sqlserver programming) as it's more likely
> to be relevant here
>
> I have a table which I have previously used for objects of a certain
> class i.e.
>
> book
>
> this table has a number of columns representing the properties of the
> book i.e number of pages, author etc.
>
> I want to be able to record an inherited object so for example I will
> have Book1_v1 and Book1_v2 - the only difference between them being the
> number of pages and the title. However Book1_v3 might be inherited from
> Book1_v2 but with a different title only while Book1_v4 might be the
> same as Book1_v3 but with a different publication date.
>
> If I copy the Book1_v1 to a new record for Book1_v2 and change the
> number of pages, if I then change the author of Book1_v1, it will not
> be reflected in Book1_v2 (and it would be difficult to do via triggers
> because you cannot be certain which fields are "overridden").
>
> Even if I have a table that says [BookId, version number, property,
> value] to override any number of properties then I am still going to
> end up with horrible joins and datatype issues and working my way back
> from v4 to v1 to get a complete row would be a nightmare.
>
> What is the solution?

Anyone who tells you they have a solution based on a sketchy newgroup post is a crank. That said, I suggest the first step toward a solution might be to avoid the First Great Blunder. Received on Wed Jun 21 2006 - 11:22:56 CDT

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