Re: what are keys and surrogates?

On 17 jan, 14:40, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Marshall wrote:
> > On Jan 10, 7:07 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
> >>Marshall wrote:
>
> >>>>Is "constructor" the same as what C. Date calls a "selector"?
>
> >>>Yes. Date calls it a selector, and the entire rest of the world
> >>>calls it a constructor. :-)
>
> >>Except "selector" has no concept of physically building anything in storage.
>
> > Okay. Just specifying a value, or a kind of value, yes?
> > That's more or less what I understand the most general
> > definition of the word "constructor" to mean. The OOP
> > world uses it a bit more specifically.
>
> I suspect the word originates in the OOP world, and it strongly suggests
> building something physical.
>
> >>>I have no strong feelings about encapsulated ADTs; what
> >>>Date calls ... uh. Shit. I can't remember what he calls them.
> >>>I don't entirely see the reason for them. Performance I guess?
>
> >>Types? Possible representations? Type generators? Only the first is an
> >>ADT, but I am curious whether you meant one of the others.
>
> > Possreps! That's the one!
>
> Having multiple possible representations for the same type allows data
> independence--especially physical independence.

You think the number of possible representations and the number of possible ways to store something in memory or on disk are related? Why?

• Jan Hidders