Re: Object-relational impedence
Date: Thu, 6 Mar 2008 11:37:51 -0800 (PST)
Message-ID: <60ec79d8-1afc-4013-8e1b-cff316d1a2b2_at_13g2000hsb.googlegroups.com>
On Mar 6, 9:39 am, S Perryman <q..._at_q.com> wrote:
> I am interested in exploring the notion of an 'ADT join' and
> how it might be implemented by an OO prog lang.
Join is indeed the most interesting operation. In the other message you dismissed projection as being covered by the concept of subclassing. Can you please be more specific? If we remove some [data] attributes, does it mean the resulting "entity" is a subclass. Then consider selection. One might be tempted to reason that it is a selection that makes a subclass by restricting to a subset of objects.
The duality between rows and columns (tuples and attributes) IMO has something to do with those pepetuum motion LSP debates. I can suggest that FCA method (which I mentioned in the very beginning of this flame war) is the right foundation for class hierarchy. Received on Thu Mar 06 2008 - 20:37:51 CET