Re: Relation Definition

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Mon, 21 Feb 2005 22:26:29 GMT
Message-ID: <petSd.17735$iW1.1311815@phobos.telenet-ops.be>

Anith Sen wrote:
>
> Reading down to the bottom of your post it seems to me like you are defining
> a relation value while Date's definition refers to a relvar, or a relation
> variable. If so, you can ignore the above since it makes sense to avoid the
> reference to typed attributes when talking about the instance of a tuple
> without a mapping function.

Ok.

>>>(1) What is exactly a "set of named typed attributes"?

>
> Precisely, a set of attribute-type pair with a name.

No, that cannot be right because it would allow the same attribute name to appear more than once.

>>>(2) The notion of n-dimensional tuple is usually reserved for ordered 
>>>tuples which is not appropriate here.

>
> Not sure in which context you are talking about dimensions here (vector
> space? N-space? ). Loosely, a tuple is n-dimensional if it has n attributes
> where n is finite. One might have a 0-dimensional tuple in a 0-ary or
> nullary relation, 1-dimensional tuple in an unary relation and so on.
>
> Can you post a reference which suggests the relevance of the n-dimensional
> tuples is usually reserved for ordered tuples?

http://mathworld.wolfram.com/n-Tuple.html

• Jan Hidders

Received on Mon Feb 21 2005 - 16:26:29 CST