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@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

Received on Mon Feb 21 2005 - 16:39:41 CST