# [DL] Question on DL negation

Matt Williams matthew.williams at cancer.org.uk
Mon Mar 5 11:45:22 CET 2007

```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
--
http://acl.icnet.uk/~mw