Re: what are keys and surrogates?
Date: Thu, 17 Jan 2008 19:55:18 -0400
Message-ID: <478feaea$0$4058$9a566e8b_at_news.aliant.net>
Jan Hidders wrote:
> On Jan 17, 10:29 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
>>Jan Hidders wrote:
>>
>>>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?
>>
>>The latter grows linearly with the former.
> > Why? Seriously. Why do you think there is a relationship at all? Why > would the number of ways a value can be represented to the user > (something which a matter of definition and/or convention) have any > bearing on how many ways there are to map it to 1's and 0's? > > -- Jan Hidders
Why do you think representations are limited to representing to users? How does representing to a user differ from representing to a machine? Received on Fri Jan 18 2008 - 00:55:18 CET