Re: Notes on 7/20 BLD draft

> >> * It seems to me a cleaner syntax is to remove existentials from 
> >> conditions and unify all quantifiers outside the rule (as with 
> >> universal now), and add a restriction in horn that existentially 
> >> quantified vars cannot appear in the conclusion.
> > 
> > The RIF Basic Condition Language is meant to be reusable also
> > (in PR and) outside the context of any rule, stand-alone (e.g.
> > for queries and integrity checking), where existentials cannot
> > be rewritten as universals in the Example 3b.->3a. manner.
> 
> Oh, you misunderstood - I did not mean eliminate existentials from the 
> syntax entirely, I meant move them outside conditions into some sort 
> of wrapper or context (like, rules).  This would make, at least, the 
> rule syntax cleaner.

Unless I misunderstood you, what you are proposing is not sound in FOL:

Exists X foo <- bar(X)

is not the same as

foo <- Exists X bar(X).



	--michael