Re: Objects and Relations

David BL wrote:

> On Feb 6, 11:04 pm, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> > On Feb 6, 12:54 pm, "David BL" <davi..._at_iinet.net.au> wrote:
> >
> >
> >
> >
> >
> > > On Feb 6, 7:26 pm, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> >
> > > > On Feb 6, 5:26 am, "David BL" <davi..._at_iinet.net.au> wrote:
> >
> > > > > On Feb 6, 12:29 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> >
> > > > > > On Feb 5, 1:25 pm, "David BL" <davi..._at_iinet.net.au> wrote:
> >
> > > > Discussion of OID's snipped because it appears we are in fact largely
> > > > agreeing that all labels are attributes - and consequently that
> > > > identity should not depend on a pointer or memory address, which is
> > > > obviously not part of the real world data.
> >
> > > Good!
> >
> > > > > > > I agree that E/R modelling should be "consigned to being an
> > > > > > > organizational tool", but again for different reasons. Unlike you I
> > > > > > > see no problem with saying entities have identity.
> >
> > > > > > I have never said that. What I have argued is that they are identified
> > > > > > by their attributes and not some imaginary hidden barcode.
> >
> > > > > I agree with that but don't see how that explains why E/R diagrams can
> > > > > be problematic.
> >
> > > > This was an argument against OID's not E/R diagrams.
> >
> > > I hadn't realised you had a different argument against E/R diagrams.
> >
> > > > The argument against E/R diagrams is trying to define what an entity /
> > > > is/. For example, if bob is married to shiela, is married_to a
> > > > relationship or an entity? And if it is an associative entity, why are
> > > > all relationships not then just entities? Or to put it a different way
> > > > (and the way much of modern philosophy views knowledge) should all
> > > > entities not just be viewed as n-ary relationships themselves? Once
> > > > you arrive at this premise, by whatever route, whether it be data
> > > > analysis, reductionism, etc, you are left with something that starts
> > > > to look incredibly like NIAM/ORM, which in turn has a natural
> > > > translation to relational modelling.
> >
> > > > > The claim that entities are illusionary or abstract
> > > > > doesn't appeal to me.
> >
> > > > Fair enough. You are incorrect, but that would be a philosophical
> > > > debate, and largely tangential to the practical issues at hand.
> > > > However it is worth noting that your standpoint is that of
> > > > essentialism, which carries little weight in modern epistimology.
> >
> > > My tendency these days is to believe that the universe (actually
> > > multiverse) only exists in a Platonic sense and physical reality is a
> > > kind of trick played on us as self-aware substructures of the
> > > multiverse. That kind of kills the whole question of what is real
> > > versus what is abstract. It seems more convenient to define
> > > everything to be real (not abstract), whether they be humans or
> > > numbers.
> >
> > > > So,
> > > > perhaps instead you could clarify what you mean by an 'entity' and
> > > > define exactly what it is, as a starter to convincing me that it is
> > > > not in fact an abstract notion. (and please try and avoid using the
> > > > word 'thing' in any such a definition).
> >
> > > Perhaps a more pertinent question is to ask you to define the
> > > difference between real and abstract.
> >
> > > It's impossible to define entity in terms of simpler notions but I can
> > > clarify my viewpoint.
> >
> > > If I point at a bunch of atoms and say "That is a human named Fred"
> > > then I consider Fred to be conceptual, mathematically imprecise but
> > > nevertheless the concept itself is real and exists in a Platonic sense
> > > (to the extent that I can meaningfully make statements about that
> > > bunch of atoms as I conceive of it as being a human named Fred).
> >
> > Well first pointing isn't allowed. One cannot continually follow Fred
> > round pointing at him all day, we need to identify to him in some
> > other way, but there I think we are agreed.
> >
> > However consider that some people's view of Fred is that Fred is Fred
> > is Fred, throughout his whole lifetime. Other people/applications may
> > need to view Fred only as he is /now/ - after all he will be composed
> > of a completely different set of atoms in a few years anyway. Then
> > there must be parts of him that make up our view of him which are
> > purely abstract, his bravery, his humour, his IQ, his body of
> > publications, etc., how should they perdure? Already the notion of
> > where he starts and finishes as an 'entity' is seriously blurring.

>

>

>


> > The old washington's axe/theseus ship paradox is perhaps a better


> > example of the concept of a well defined entity being insufficient. I

> > am sure you know it -  "In a museum somewhere there is the axe used by

> > washington. Ok, the handles been changed a few times. Oh and so has

> > the headstock, but hey... its still the same axe". Same 'axe entity',

>

>


> > But this problem is not really a paradox at all if you just discard

>

>


> > That's again why I believe one should always


> > consider communicated propositions (which we have a shared common

> > understanding of). Then you it becomes clear that the axe is the same

> > axe if propositions discussing it use its name as the primary key. It

>

>

This thread should then now probably belong on a philosphy board, but hey, its been interesting.

> I note as well that Godel's theorems should not be interpreted as
> favoring formalism over realism. On the contrary I see it as
> revealing a limitation of formalism. In fact Godel himself was a
> Platonist.

You have invoked Godel's law. This is the cdt equivalent of Godwin's Law which states that as a usenet thread approaches infinity, the chance of that thread mentioning Hitler becomes 1 (i.e. a certainty). It's generally agreed upon that when this happens, the thread is over, and the person mentioning Nazis losing the discussion.

Here it seems to be Godel ;)

>


> > The purpose of this is not anal philosophising. Imo philosophy is

>

>


> > And in this Codd's approach is genius, because this entity-

> > less philosophy underpins his original RM, and we've seen it actually /

> > applies/ to solving real world data handling problems. Enough that it


> > even seems possible to help me store information about employees _and_

> > solve the Theseus Ship paradox in terms of RM keys. And unlike OO,

>

>


> > > As


> > > a Platonist I don't like to say that the entity labelled Fred is

> > > abstract.  Instead I say it is real because I define all (reasonable)

> > > mathematical notions to be real, whether they map back to atoms around

> > > me or not.  I say something physically exists if there is a mapping

> > > back to atoms.

> >

> > Fair enough, but I don't really care if your a platonist, a

> > reductionist, a mereological nihilist or a senior gynaecologist (and

> > trust me compared to practicitioners like Gene and Marshall, I'm

> > positively wooly). A philosophy is only worth its salt here if it has

> > practical positive impact.

> >

> > > Entities are always real (ie exist) but they may or

> > > may not physically exist.   I note that the definition of physical

> > > existence is dependent on the observer as a self-aware substructure in

> > > a multiverse.

> >

> > So you object to me saying "entitities are abstract" by saying that

>

>


>     Consider a web server.  This can be seen at a number


>     of different "levels of abstraction"  [snip]

>     All of these "levels of abstraction" are equally valid.

>     I don't want to get into boring discussions about what's

>     physical versus logical, model versus what is modeled,

>     or real versus abstract

>