Re: Mixing OO and DB

From: Dmitry A. Kazakov <mailbox_at_dmitry-kazakov.de>
Date: Mon, 18 Feb 2008 09:40:49 +0100
Message-ID: <vgothc82wd92$.qqcciqghcdlz$.dlg_at_40tude.net>

On Sun, 17 Feb 2008 21:24:54 +0100, mAsterdam wrote:

> More about inconsistencies as a feature - do you have a
> special reason to go into that?

Just to show that if you want to reject something you need to measure its inconsistency first, by deriving true and false, for example.

>>> A dedicated datacapture process needs to be
>>> aware of the schema, and eventually of the current data.
>>> Rendering also benefits from schema awareness.
>> 
>> Oh, that's simple. The process yields the value of given type. 

> Schema seen as type?

As a set of types.

>> That's all it need to care. 
>> If an integer number range 1..35 is expected, then it is
>> illegal to return 100 or string. 

> Not, appearantly.
>

>> Contract is only meaning.
> Lost in translation. Please rephrase.

The type describes value semantics ("meaning") within the formal system. Everything that matches the type is meaningful inside it.

Admittedly, there can be types we could not model/handle in a Turing complete language. So, what I have in mind is to use a typed language for informal common ground and its much weaker formal variant for programming.

>>>>>>>>>>>> Yes, we cannot reason about meaning while staying 
>>>>>>>>>>>> within the same formal system. Because you seem 
>>>>>>>>>>>> to bind data with a meaning (as I do), that immediately
>>>>>>>>>>>> kicks the notion of data out of the formal system. 
>>> (retry) Indeed. However, we can have a shared, formal proxy to
>>> meaning. Date's external predicates are a good starting point
>>> for that.
>> 
>> See above. IMO it the responsibility of a type system to make it possible
>> to express constraints (when new types are obtained by constraining). 

>
> I have to guess what you mean, here.
> Is *Type* what you propose as shared, formal proxy to meaning?

Yes.

>> This is not the only way though, you need also
>> other operations in types algebra.

>
> Way to do what?

To create new types. There exist type operations beyond constraining.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Received on Mon Feb 18 2008 - 09:40:49 CET