RE: [BLD] Frame without slot/value pair?

Surprisingly, in BREs, testing for "existence" is not too uncommon.
Usually when loading "dirty records" from a DB or somesuch, you might
say 
if t != null and {rest of rule conditions} then ...

Another typical use is that I have a (poorly maintained) array of
objects. If I process them one-by-one, I might want to check the
references actually exist...

[Of course, I am talking about operational not logical systems :) ]

Paul Vincent
TIBCO | ETG/Business Rules 
 

> -----Original Message-----
> From: public-rif-wg-request@w3.org
[mailto:public-rif-wg-request@w3.org]
> On Behalf Of Christian de Sainte Marie
> Sent: 04 January 2008 19:47
> To: Michael Kifer
> Cc: Boley, Harold; RIF WG
> Subject: Re: [BLD] Frame without slot/value pair?
> 
> 
> Michael Kifer wrote:
> >
> > [...]  Formulas like t[] are also useful. If they are allowed, their
> > semantics is that the object t exists (without testing any of its
> > properties).
> 
> Hmmm. I wonder how useful it is really.
> 
> In order to check the existence of object t, you have to denote it in
> some way: How do you denote an object without either asserting or
> checking its existence already in the process (thus removing any need
to
> check it further)?
> 
> Actually, the only use I found for a formula like t[] is to allow the
> retraction of an individual without having to allow retracting TERMs
as
> well as ATOMICs (in RIF-PRD). But that's a different can of worms...
> 
> Christian
>