Re: what are keys and surrogates?

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 17 Jan 2008 17:29:38 -0400
Message-ID: <478fc8c5$0$4059$9a566e8b_at_news.aliant.net>


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. Received on Thu Jan 17 2008 - 22:29:38 CET

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