Re: Trying to define Surrogates

"JOG" <jog_at_cs.nott.ac.uk> wrote in message news:1155947515.920269.149070_at_p79g2000cwp.googlegroups.com...
>A few useful things have also come up for in the process of thinking
>about this:
>
>1) It has cemented in my mind the knowledge that identification is what
>matters in data modelling, not identity. i.e. I can see two things are
>different, but if I want to talk about them, identification of that
>difference is the vital aspect. i.e.
>
>Ex Ey isCow(x) & isCow(y) & ¬x=y
>
>maybe be perfectly /true/ but it is of little use unless I am able to
>identify how ¬x=y.
>

So. Identity and identification are different things. I'll buy that. Identification is the result of what someone did to distinguish one thing from all others; Identity is what something has that distinguishes it from all others. Identification is a symbol that someone assigned to something; identity is what they used to distinguish something so that they could make the assignment. I think that the frame of reference is critical. The important differences between identification and identity are that identification doesn't change, but it's tied to the observation, and that the perception of identity depends on the frame of reference. Two people can assign different identification to something, or the same person may assign different identification at different times. For example, Borders may have assigned the symbol 1324326 to you, whereas Sears assigned 3215131, or Borders may assign the symbol 1214123 to you at a later date. Also something can appear different at different times and still be distinguishable from all other things at each point in time. For example, you could be fifth in line at the bank at 3:00pm and third in line at 3:05pm.

>2) All items can be distinguished, if ultimately by nothing else than
>their location. In fact even change can be accounted for by identifying
>an item by its path in space over its lifetime. A magical identity (or
>genidentity, or perdurance, or whatever) is metaphysical nonsense.
>

How do you articulate that path and associate it with the item under discussion? Also, two items can occupy the same space at a particular instant or during an interval--even the entire lifetime, especially if one is part of the other. How do you differentiate between them?

>3) Duplicate propositions are so wrong it hurts my head to think about
>them. I obviously understood this before in terms of the definition of
>a set, but now doubly so in the context of identification.
>
>4) Lists don't belong at the lowest level of modelling. The items in a
>list are not duplicates even if they appear so. The 5th head in a list
>of coin throwing results is not the same thing as the first. It has
>distinguishing attributes, the time it occurred for instance, or the
>item that preceded it.
>
>5) oid's are a nonsense in terms of data modelling. Distinguishing an
>assertion by pointing at it continually cannot be shared by a new
>observer (and so is of no use to databases) and is unnecessary given
>(2). It would be like trying to keep track of the identity of cans of
>campbells soup by pointing at them. You're going to run out of hands
>very quickly and you're in /serious/ trouble if you ever want a beer.
>

oid's don't identify assertions, they identify what the assertions are about. They are a symbol for the endurant essense of something--an articulation of the path of the thing through spacetime, perhaps. There appears to be a lot of confusion about this. A database is knowledge about things; it is not a representation of things. That's the difference between a database and an object store. A database is a set of propositions about things; an object store is a set of representations of things. A candidate key can only identify something indirectly. It identifies the proposition about something. An oid, on the other hand, identifies something directly. The extra level of indirection is important.

>I know some of these things are intuitive to many on cdt, but I find it
>useful to know these conclusions can arise from examining exactly what
>identity and identification mean.
Received on Sat Aug 19 2006 - 06:22:43 CEST