Re: Relation Definition
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Mon, 21 Feb 2005 22:39:41 GMT
Message-ID: <NqtSd.17741$JY2.1416228_at_phobos.telenet-ops.be>
>
> Yes. Or just "attribute name".
>
>
> But tuples don't have columns, and you have not defined what a column
> is.
Date: Mon, 21 Feb 2005 22:39:41 GMT
Message-ID: <NqtSd.17741$JY2.1416228_at_phobos.telenet-ops.be>
Alfredo Novoa wrote:
> On Fri, 18 Feb 2005 21:33:50 GMT, Jan Hidders
> <jan.hidders_at_REMOVETHIS.pandora.be> wrote:
>
>
>>>>Def. [Tuple] A *tuple* is a partial function that maps column names to >>>>domain values and is defined for a finite set of column names which is >>>>called its *header*. >>> >>> >>>In which way is "columnar" a tuple "column"? >> >>You mean, why did I say "column name" and not just "field name"?
>
> Yes. Or just "attribute name".
>
>>Because >> the field names in these tuples must be valid column names.
>
> But tuples don't have columns, and you have not defined what a column
> is.
That is not necessary. All that is required is that the set of column names is postulated and described in advance. But as far as I am concerned you can also call them "attribute name" if you like.
> BTW a header is not a set of column or attribute names, it is a set of
> name and domain pairs.
That's a matter of definition. Note that I was not speaking of headers of relations but of headers of tuples, which is something else.
- Jan Hidders