Re: model inherited object

deja_at_2bytes.co.uk wrote:
> actually the other databases are irrelevant - in a single database I
> want to be able to select the "view" of an object at a certain date. I
> am suggesting to record the "history" of an object as it changes with
> one row per change BUT ideally I want that history record to only show
> the change in the relevant attributes and indicate that the other
> attributes are "inherited" from whatever the previous record value was
> AND to somehow make the view of an object at any given date not too
> complex (this model would seem to require quite a complex select)
>
> I could have a history table for each attribute but that gets rather
> busy and complicated when it could be many tables x many attributes. Or
> I might just have the limitation that once you override a record for a
> year i.e increase the size of the room in 2007, any further changes to
> previous years will need to be manually duplicated in 2007 (and any
> other overrides) - though this is not ideal.
>
> The current system basically has an entire set of data for each period
> independent of each other.
> 1) that means recreating the location data every time a new period is
> created
> 2)any change to the location data in one year is not automatically
> reflected in later years

Once again, your data model is temporal. Temporal queries are complex enough even in the case when you have a straightforward model

<col1, col2, col3, ..., valid_from, valid_until>

http://www.sigmod.org/sigmod/record/issues/0606/p16-article-zimanyi.pdf

I suggest that the effort you put into optimizing this model (by recording oly those fields that change) would be wasted by increasing complexity of the queries against your model. Received on Wed Jun 21 2006 - 23:13:20 CEST