help with understand equality ?

• From: Lena Lau <llau@vistology.com>
• Date: Tue, 6 Sep 2011 11:20:06 -0400
• To: public-rif-dev@w3.org
• Message-ID: <CAB=EOC2WyyG3XwyB+NbfVkEnoKM+N8ZqPk7VoUVzVKEmEq+WjA@mail.gmail.com>

Hi

I am new to RIF and I am trying to follow the example 8, in section
4.2 of  http://www.w3.org/TR/2010/REC-rif-bld-20100622/

In this example, the usage of equality is unclear to me. It seems like
in the example,
the ?diffduration is assigned the value of a function.
However, I am under the impression (from the rest of the document)
that equality is testing whether 2 terms are equal.

Forall ?item ?deliverydate ?scheduledate ?diffduration ?diffdays (
       cpt:reject(<John> ?item) :-
           And(cpt:perishable(?item)
               cpt:delivered(?item ?deliverydate <John>)
               cpt:scheduled(?item ?scheduledate)
               ?diffduration =
External(func:subtract-dateTimes(?deliverydate ?scheduledate))
               ?diffdays = External(func:days-from-duration(?diffduration))
               External(pred:numeric-greater-than(?diffdays 10)))
   )

I hope that this is the right mailing list to post to.
Could someone help me understand how equality is used.

Thanks you.

Received on Tuesday, 6 September 2011 16:13:48 UTC