Re: [TED] Action-188, ISSUE: production rule systems have "difficulty" with recursive rules in RIF Core

>>> At the moment, unless some new information comes along, I'm inclined 
to
>>> agree that we need to leave recursive Horn rules out of the core.
>> 
>> All of the rule sets that I use for my practical work have
>> some rules that are recursive, even some of them also have
>> mutual predicate dependency like
>>   pred3(X,Z):- pred1(X,Y), pred2(Y,Z).
>>   pred2(X,Z):- pred3(X,Y), pred4(Y,Z).
>
> I suspect all "power users" of rule systems use recursive rules and
> would need to use a more powerful dialect than RIF Core.

Well, depends, but I consider working with e.g. rdf collections
to find member items not really "power use"..

{?LIST rdf:first ?ITEM} => {?ITEM list:in ?LIST}.
{?LIST rdf:rest ?REST. ?ITEM list:in ?REST} => {?ITEM list:in ?LIST}.

nor examples like

{?X eg:ancestor ?Y} => {?Y eg:descendant ?X}.
{?X eg:descendant ?Y} => {?Y eg:ancestor ?X}.
{?X eg:ancestor ?Y. ?Y eg:ancestor ?Z} => {?X eg:ancestor ?Z}.


-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/