- From: Gary Hallmark <gary.hallmark@oracle.com>
- Date: Tue, 02 Sep 2008 14:35:51 -0700
- To: rif WG <public-rif-wg@w3.org>
At today's telecon we discussed object creation. Christian and Patrick wonder how one obtains a reference to the new object. I.e. how to support the following use case (expressed in FLD): Forall ?x (Exists ?y ?z And(?y # _Y ?z # _Z ?y[_z->?z] ?z[_x->?x]) :- ?x # _X) The proposed syntax 'new' CLASS '[' (TERM '->' TERM)* ']' provides no good way to do this. I see several options: Option A. 'new' [Var '#'] CLASS '[' (TERM '->' TERM)* ']' e.g. Forall ?x ?z (Do(new ?z # _Z[_x->?x] new _Y[_z->?z]) :- ?x # _X) The Var ?z must be declared somewhere, presumably in the enclosing Forall. What happens if the Var is also referenced in the rule condition? Option B. Use the FLD syntax for PRD. The concern is that this is overly general and thus PRD would have many hard to specify restrictions on the use of Exists in a conclusion. Option C. use a builtin (e.g. rif:new) so that object creation could be in core. E.g. Forall ?x (And(rif:new(1 ?x) # _Z rif:new(1 ?x)[_x->?x] rif:new(2 ?x) # _Y rif:new(2 ?x)[_z->rif:new(1 ?x]) :- ?x # _X) There are n+1 arguments to rif:new. The n Forall variables and one "occurrence number". There are m distinct occurrence numbers per ruleset, where m is the number of existential variables in the ruleset that are "skolemized". In the above, n=1 and m=2. Note that rif:new has variable arity (n+1). The drawback of option C is that production rule engines don't typically provide rif:new as a function. A PRD translator would find it very difficult to translate rif:new in a condition, or indeed in an action except for when used in membership with a Class Constant and in frames. Also, PRD would need to support And() and "#" in conclusions, but "#" only in the case where the left side is rif:new...
Received on Tuesday, 2 September 2008 21:37:19 UTC