Re: Object-relational impedence

From: Bob Badour <>
Date: Tue, 11 Mar 2008 18:19:06 -0300
Message-ID: <47d6f750$0$4076$>

TroyK wrote:

> On Mar 10, 4:53 pm, Bob Badour <> wrote:

>>TroyK wrote:
>>>On Mar 8, 7:09 am, (rpost) wrote:
>>>>TroyK wrote:
>>>>>Who said anything about stored procedures? I'm talking about
>>>>>implementing the business rules via constraint declaration in the
>>>>>database, and deriving new values throught the application of SQL
>>>>Do you also treat dynamic constraints in this way?
>>>>E.g. "unless otherwise specified, an employee shall get a 2%
>>>>salary increase after each full year of employment".
>>with not_excluded_ee = (
>> employees join ( employees{ee#} minus excluded_ees{ee#} )
>>), increases = extend (
>> not_excluded_ee where is_anniversary_period(pay_period(now),hire_date)
>>) add increase = salary * percent(2)
>>>>Or: "two movable 3D shapes shall never collide; collision is avoided
>>>>by the following repositioning algorithm that is guaranteed
>>>>to pull all objects apart that get too close: (...), however, this
>>>>algorithm may be replaced with another that has the same property".
>>with other_objects = objects rename all prepending "other_"
>>, collisions = objects join other_objects
>> where rank_attrib < other_rank_attrib
>> and min_distance(polygons,other_polygons) < threshold_distance
>>, while exists(collisions) {
>> update collisions
>> set position = ...
>> , other_position = ...
>>>Inferring the definition of "dynamic constraint" from your examples,
>>>in the first, I think that it would be sufficient to model and record
>>>whatever attribute means "otherwise specified" and include that as
>>>part of the condition in the constraint declaration.
>>What was the constraint part again?
> I suppose given a db that maintains some temporal dimension for the
> employee facts ("history table" or somesuch) would have a constraint
> that the tuples within it must be derived using your expression above.
> Absent that, the expression itself constrains the values that can be
> derived. Is that a fair statement?

Oh, you mean a constraint like:

( ee# in excluded_ees{ee#} )
or ( not is_anniversary_period(pay_period(now),hire_date) ) or ( salary >= previous_salary * percent(1.02) )

What's so hard about that? Note, I used >= to allow for other coincidental raises.

>>>I haven't had occasion to apply the technique to anything more complex
>>>than such an example, so I'll have to say "I don't know" to the 3D

> Nice sketch of the 3D solution, Bob. I've set aside some time to play
> with SQL Server's new spatial datatypes (Geography and Geometry), but
> this cut of the feature only supports 2D.

Thank you. I hope you have fun with the spatial datatypes, but I wish you had a nicer language than SQL for playing with them. Received on Tue Mar 11 2008 - 22:19:06 CET

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