Re: Is a function a relation?

On Jun 23, 11:44 am, David BL <davi..._at_iinet.net.au> wrote:

> Consider the binary relation with the following graph
>
> { (x,y) | y = x+1 }
>

I neglected an important assumption: As is customary in the database community, it is assumed that the attributes of a relation are identified by name, not by ordinal position (i.e. despite my use of ordered pairs above - which was for only for convenience).

I should have instead defined the body of the relation as:

    { t | t('y') = t('x') + 1 }

where each t is a tuple, formalised as a mapping from attribute name to attribute value. Received on Tue Jun 23 2009 - 06:42:41 CEST