Re: On view updating
Date: Sun, 26 Sep 2004 09:45:57 +0200
Message-ID: <415673b6$0$25965$e4fe514c_at_news.xs4all.nl>
Alfredo Novoa wrote:
> mAsterdam wrote:
>>The consequence is that many lengthy misunderstandings >>can be avoided by immediately giving a clear >>definition of some crucial terms whenever used >>in a discussion which goes beyond one of those groups. >>Define it for the discussion at hand. >>My hope is that new, more broadly used definitions >>will arise.
>
> I agree. Fortunately we have dictionaries and institutes of standards.
They *do* help. There are topics though where there are competing dictionaries though, one group takes one set of dictionaries etc...
>>My statement asserts several things in one go, >>but most importantly: that 'type' is one of the >>words that has its meaning bend and twisted >>(jargonised) subtly differently in different >>groups. I call it a non-problem, because I suspect >>the jargon differences cover up some real, >>perception of subjectmatter related (instead of >>just the labeling), interesting problems.
>
>
> My obvious sugestion is that we should resort to the authoritative
> references:
>
> http://www.nist.gov/dads/HTML/abstractDataType.html
Heh. It has the definition I am currently questioning. It smells.
But yes. Thing is: if you want to challenge those definitions you'll have to be explicit about it.
>>>They are intended to be shorthands for expressions, but they are not >>>syntactic shorthands because they are database objects. Views exist in >>>the database catalog. >> >>Syntactic shorthands cannot exist within the database catalog?
>
> No, it makes no sense. A syntactic shorthand is only an alternative
> and shorter way to say something, and not an alternative way to
> achieve a desired result.
>
>
>>>Both groups of statements have different semantics therefore a view is >>>not a syntactic shorthand. >> >>If the deletion of 'r where a > 10' is a common thing to do, >>then var v makes database A easier in use than database B.
>
>
> Indeed, not all shorthands are syntactic.
Ah... ok. Shorthand yes, if you really want to see it that way, but syntactic no. Maybe things like this is why some distinguish a sigmatic layer between syntactic and semantic. I could not find a good reference to look into that, though.
>>Assuming var r has the same semantics and values in both databases, >>both databases reflect the same facts. >>This is true before and after the deletes.
>
> Indeed, but the statements have different meanings, and syntactic
> shorthands only affect to the syntax, and never to the meaning.
Yep.
> For instance:
>
> a := a + 5;
>
> is not a syntactic shorthand for this:
>
> for i := 1 to 5;
> a := a + 1;
>
> The result is the same, but we are not saying the same.
IOW: semantically different, pragmatically the same.
>>>delete a union b;
>>>
>>>or
>>>
>>>var r relation { a integer }
>>> key { a }
>>> foreign key { a } references a union b;
>>
>>This puzzles me. From 'delete a union b;' I took the suggestion
>>that a and b where both relational variables.
>
> Yes.
>
>>In the second >>statement a is a declared integer in the first line, >>and what is a in the tail of the 3rd line of the second statement?
>
>
> The same relation variable as in 'delete a union b'.
>
> In relational databases is frequent to have relvars and attributes
> with the same name,
> but I should have used a different name, sorry.
Heh. Yes, that helps in examples. Thank you. Received on Sun Sep 26 2004 - 09:45:57 CEST