[sc34wg3] TMQL: Navigation "traverse"

[Robert Barta]

On Sun, Jul 20, 2008 at 02:53:27PM +0200, Lars Heuer wrote:
> Comments against TMQL draft dtd. 2008-07-15.
> 
> 4.4 Navigation
> ==============
> 
> traverse
> --------
> 
>     "[...] whereby the incoming topic is deducted once from that
>     sequence [...]"
> 
> I wonder why "once" is mentioned: If the incoming topic is deducted
> (does not appear at all) from the sequence, "once" should be removed.
> In case the "once" is intentional: Why should the topic which plays n
> roles occur n - 1 times in the sequence?

"once" is intentional.

Consider this:

 write-paper (author: lheuer, author: rho, editor: lheuer)

Then I would expect to see { lheuer, rho } as result of

 lheuer <-> write-paper

I would even argue that one lheuer should be in the result here:

 write-paper (author: lheuer, author: rho, author: lheuer)

ALL (!) semantics in TMQL is multi-set (bag) based. So this should
definitely not be an exception.

If someone wants to make things unique, then there is a predefined
function 'uniq'.

\rho