# [DL] Question on DL negation

Maurizio Lenzerini lenzerini at dis.uniroma1.it
Fri Mar 23 11:33:49 CET 2007

```I am not sure I understand your question. However, rules with one
negated atom in the head are typically disjointness constraints
(asserting that a set of predicates do not have common instances), and
usually introducing these constraints in a DL is not complex.

Matt Williams ha scritto:
> Dear All,
>
> As I understand, most DL's do not allow for the negation of roles.
>
> However, given a formula of the form R(x,y) (where R is some role),
> since this is equivalent to (R(x,y) & \top(y)) which could be negated as
> ¬( R(x,y) & \top(y)), is it possible to effectively relax this
> constraint in some cases without affecting the logic?
>
> I'm interested in rules that have a single role as the head, and
> negation of such heads would be useful...
>
> Thanks,
>
> Matt

--
Maurizio

------------------------------------------------------------
Prof. Maurizio Lenzerini
Dipartimento di Informatica e Sistemistica "Antonio Ruberti"
Università degli Studi di Roma "La Sapienza"
Via Salaria 113,  I-00198  Roma,  Italy
Tel:       +39 - 06 - 8841954
Fax:       +39 - 06 - 85300849
E-mail:    lenzerini at dis.uniroma1.it