Re: views of binary operations

From: paul c <toledobythesea_at_oohay.ac>
Date: Mon, 17 Jul 2006 14:36:09 GMT
Message-ID: <tfNug.200176$IK3.77245@pd7tw1no>

Bob Badour wrote:

> Aloha Kakuikanu wrote:

>> Marshall wrote:
>>
>>> Aloha Kakuikanu wrote:
>>>
>>>> Marshall wrote:
>>>>
>>>>> Consider named views of binary operations on relations.
>>>>>
>>>>> Given a relational operator "op" and relation variables A and B,
>>>>> and a declaration of:
>>>>>
>>>>> r = A op B
>>>>>
>>>>> the language evaluates the expression "A op B" and assigns the
>>>>> result to r.
>>>>>
>>>>> However, if we declare this as a view, ...
>>>>
>>>> View is a named expression. r is a view.
>>>
>>> Is it necessarily named? Might we find use for an anonymous view?
>>
>> Well, the point is that the term "view" is redundant and SQL-ish.
>> Relations and relational expressions are the fundamental concepts, and
>> view is some bastardized idea.

> 
> I disagree. Views and snapshots are fundamental and are the source of 
> logical independence.

Not familiar with the term 'logical independence' as written - does it refer to logical-physical independence and/or lack of redundancy?

(I notice that Codd 1970 mentioned the word 'view' several times, I think once as a synonym for model and also in non-specific terms but not in language terms, say as a named relational expression or catalogue macro, ie. not in today's sense, if I've got it right. As a 'macro', a view already defers some evaluation, if that's what Marshall S. is driving at. Maybe that's not important, after all what we call relations today he called relationships then.)

p Received on Mon Jul 17 2006 - 09:36:09 CDT