[DL] Horn clauses and DLs

Rodrigo de Salvo Braz braz at uiuc.edu
Fri Oct 1 17:15:34 CEST 2004

On Fri, 1 Oct 2004, Alex Borgida wrote:

> shows that the two techniques are incomparable. (Prolog cannot encode
> disjunction, which is easily encoded in DLs. While DL's cannot encode
>  p:- e(x1,x2),e(x1,x3),... with all permutations of x_i and x_j
> combinations.

Thanks. I didn't mean to say that there was a containment relationship
between some DL language and Horn clauses. But there isn't such a
relationship between many pairs of different DLs also.

The reason I am asking this is because I get the feeling from many people
that if you have some practical application in which you want a tractable
language, then you should immediately restrict yourself to choosing from
DL languages. I question this, and think that Horn should also be included
as one of the options. Sure, it has its own tradeoffs that have to be
considered, but I don't see a *a priori* reason to rule it out. That's why
I am writing, to check if people in this list can give me such a reason.



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