PRD - errors in presentation syntax example

RIF PRD Recommendation 22 June 2010

There are several errors in the presentation syntax of the ‘running example’ given in Example 9.1.   I have described these in the attached  document together with some additional minor issues concerning the grammar.

Here is a corrected version that parses successfully according to the EBNF productions provided in the specification.

Document(

Prefix( ex1 <http://example.com/2009/prd2> )

(* ex1:CheckoutRuleset *)
Group rif:forwardChaining (
   (* ex1:GoldRule *)
   Group 10 (
     Forall ?customer such that And(?customer # ex1:Customer
                                    ?customer[ex1:status->"Silver"])
       (Forall ?shoppingCart such that ?customer[ex1:shoppingCart->?shoppingCart]
          (If Exists ?value (And(?shoppingCart[ex1:value->?value]
                                 External(pred:numeric-greater-than-or-equal(?value 2000))))
           Then Do(Modify(?customer[ex1:status->"Gold"])))))

   (* ex1:DiscountRule *)
   Group (
     Forall ?customer such that And(?customer # ex1:Customer )
       (If Or( ?customer[ex1:status->"Silver"]
               ?customer[ex1:status->"Gold"])
        Then Do ((?s ?customer[ex1:shoppingCart-> ?s])
                 (?v ?s[ex1:value->?v])
                 Modify(?s [ex1:value->External(func:numeric-multiply (?v 0.95))]))))

   (* ex1:NewCustomerAndWidgetRule *)
   Group (
     Forall ?customer such that And(?customer # ex1:Customer
                                     ?customer[ex1:status->"New"] )
       (If Exists ?shoppingCart ?item
                  (And(?customer[ex1:shoppingCart->?shoppingCart]
                       ?shoppingCart[ex1:containsItem->?item]
                       ?item # ex1:Widget ) )
        Then Do( (?s ?customer[ex1:shoppingCart->?s])
                 (?val ?s[ex1:value->?val])
                 (?voucher ?customer[ex1:voucher->?voucher])
                 Retract(?customer[ex1:voucher->?voucher])
                 Retract(?voucher)
                 Modify(?s[ex1:value->External(func:numeric-multiply(?val 0.90))]))))

   (* ex1:UnknownStatusRule *)
   Group (
     Forall ?customer such that ?customer # ex1:Customer
       (If Not(Exists ?status
                      (And(?customer[ex1:status->?status]
                           External(pred:list-contains(List("New" "Bronze" "Silver" "Gold") ?status)) )))
        Then Do( Execute(act:print(External(func:concat("New customer: " ?customer))))
                 Assert(?customer[ex1:status->"New"]))))
  )
)


Regards

Charles
Charles Young
Principal Consultant

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