[DL] Horn clauses and DLs

[Rodrigo de Salvo Braz]

On Sun, 10 Oct 2004, Enrico Franconi wrote:

> I really mean structured syntax - where this argument is not as trivial
> as it seems.
> On the one hand, there are all the long standing arguments from
> cognitive science showing that "frames/features" are a basic
> representation mean for humans; this started all the KL-One and
> derivative stuff (up to DLs). So DLs can be used in a intuitive way by
> humans for KR.

Couldn't it be that this issue is orthogonal to the distinction between
Horn clauses (or more generally rules) and DLs? It seems to me that Horn
clauses could also be expressed with a more intuitive structured syntax.
Something like:

father(X,Y), father(Y,Z), father(Y, W) => grandfather(X,Z), sibling(Z,W)

written as

X father father Z, X father father W => X grandfather Z, Z sibling W.

etc.

Some expert systems (Flex comes to mind) have elaborate structure syntax
doing that and rely on rules at the end.

> On the other hand, there is the more recent argument from logicians
> such as van Benthem, Gabbay, Vardi et al, about the "guarded fragment"
> (GF) of FOL being the "right" fragment of FOL - DLs are just a special
> interesting case of the GF. See, e.g., "The Guarded Fragment: Ins and

That sounds interesting, I have to learn about it.

Thanks,

Rodrigo