RE: Does the expressive power of SPARQL include all forms of default negation?

On Wed, 2009-09-02 at 09:31 +0000, Seaborne, Andy wrote:
[...]
> 
> One possibility the working group is considering is NOT EXISTS (also known as UNSAID)
> 
> PREFIX :        <http://example/> 
> 
> SELECT *
> {
>    ?x a ?t 
>    NOT EXISTS { ?x a :C }
> }
> 
> -----------
> | x  | t  |
> ===========
> | :b | :D |
> -----------
> 
> Which I think is easier to read.

The irony is kinda thick... we looked at UNSAID
in Jan 2005 too...
 http://www.w3.org/2001/sw/DataAccess/ftf4.html#item04

The arguments for BOUND over UNSAID included
  "users were less likely to write difficult-to-optimize queries
  with UNSAID."

well, yeah... users are less likely to use mystifying features. ;-)

The next argument was:

  "BOUND seemed easier to teach and learn to several WG members,
  as well."

That seemed counter-intuitive to me at the time, but there
wasn't much to go on at the time.
Since then, if experience has shown me/us anything, it's that
BOUND is _not_ easy to teach and learn.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
gpg D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E