Re: Relation Definition

Dawn M. Wolthuis wrote:
>
> As data structures, unordered tuples would be bags/multisets (and possibly
> sets), is that correct? The reason not to call them that is because of the
> additional information about the domain from which each element comes,
> perhaps?

Not really. An unordered tuple is defined here as a finite partial function that maps field names to values. So an example is

   { (a, 1), (b, "true") }

which you write usually more like

   ( a : 1, b : "true" )

You can see how this is a generalization of the usual notion of tuple since an ordered pair can be modeled by such a finite partial function if its domain (the field names on whic it is defined) happens to be the set {1, 2}.

• Jan Hidders