Re: Objects and Relations

On Feb 13, 6:49 pm, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> On Feb 13, 1:35 am, "David BL" <davi..._at_iinet.net.au> wrote:

I have appreciated your feedback.

The most important question is whether the conjecture is coherent (or can be made coherent). I believe I need to gain a deeper understanding of your perspective.

[snip]

> > 1. In the design entities can be classified as inside or outside the
> > abstract machine
>
> RM does not take this view. It is not concerned with 'entities', but
> facts - propositions composed of roles and values.

I believe I understand what roles and values mean, but I don't appreciate the importance of the distinction you are making.

My feeling is that my conjecture is comparatively easy to understand for OO and far less clear what it means for RM. My original post went to the trouble to go through a number of OO examples to illustrate its meaning, but the RM side was largely ignored.

Curiously you are the only one that has claimed that the conjecture itself is ill defined. In fact Marshall seemed to indicate that the distinction between internal and external entities was meaningful, but perhaps the real issue is that the conjecture was buried in the original post and not stated very clearly.

I presume it is always possible for a proposition to be stated in natural language. My feeling is (and I admit this is pretty vague) that the nouns can be regarded as entity identifiers. For this reason I find it very strange to declare facts and yet claim there are no entities to which they apply. Is this what you are implying or do I misunderstand?

I've been thinking about the following example: There is a collection of Lego pieces and we want to store information about how they have been connected in various configurations. An interesting question is whether we try to distinguish pieces that for all intensive purposes look the same. It would appear not, otherwise we will be forced to get out a felt tip pen and give them unique identifiers, and we don't want to do that. Therefore a particular piece is only described (but not uniquely identified) by its attributes (eg its colour and dimensions). This all sounds well and good. Unfortunately I don't see how we are going to store the information about what is connected to what unless we identify the pieces themselves. This is an unfortunate paradox. On the one hand we need to uniquely identify the pieces in order to represent the structure, and on the other hand, at some higher level we aren't at all interested in the identity of the pieces.

There seems to be some relationship back to value types. The equivalence test of value types with internal structure is based on whether the structures are isomorphic. The identity of the items within the internal structures is ignored.

Interestingly an isomorphism test for two given configurations of Lego pieces sounds useful.

Can you shed any light on what this means? Received on Wed Feb 14 2007 - 05:51:50 CET