Re: Objects and Relations

On Feb 7, 8:12 pm, "David BL" <davi..._at_iinet.net.au> wrote: <snip>
> The semantics of Clone at the problem domain level is generally
> unambiguous except in its scope (in the sense of has-a relationships
> to other objects). It always means making a copy of the object such
> that it has the same attributes but a different identity. This makes
> sense for a class named EmployeeModel, but not for a class named
> Employee.

<snip>
> The idea that you look at entities (let's just call them nouns if you
> like) and ask whether they are part of the abstract machine is simple
> yet important because it neatly explains, without meta-physical mumbo
> jumbo the non-overlapping difference in scope of RM and OO.

When I have worked with architects who have prepared models as blueprints and they point to their model of a doorway, they call it a doorway. They similarly use the terms "room" and "wall." There is no confusion at all. I understand they are pointing to a model of a room and calling it a room. Similarly with software. There is absolutely no reason whatsoever not to name the components of your model after that which they are modeling.

As for the scope of RM and OO, there is obviously an overlapping scope. The question is not whether one can persist data using one model for the data or another, but what the pros and cons are for using either or using some other model. Given a typical software application, one could choose to use an OO model, a multivalued model (Nelson-Pick model), a relational model, or a codasyl model, for example, for the development of this software application. I think that shows some overlap in scope, don't you? --dawn Received on Thu Feb 08 2007 - 05:04:51 CET