Re: Is a function a relation?

From: David BL <>
Date: Mon, 22 Jun 2009 21:42:41 -0700 (PDT)
Message-ID: <>

On Jun 23, 11:44 am, David BL <> 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

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