I am trying to capture a conflict using SWRL rules. I learned that SWRL do support rules with empty head(consequent). But the Protege does not allow defining such rules. A dummy example of what I am trying to achieve is
Person(?x)^hasSon(?x,?y)^hasDaughter(?x,?y)->
Meaning that it is not possible that a person can be linked with a same individual both by hasSon and hasDaughter properties. If it is not possible in protege, please guide me on how to achieve this alternatively.
The rule body can be empty, but it does not imply a contradiction, as in your intentions; it is interpreted as the rule not applying. The specs are here.
If I understand your intent correctly, what you are after can be achieved by creating two classes: define an exact cardinality restriction of 0 for hasSon and an exact cardinality restriction of 0 for hasDaughter, then assign these classes as range of hasDaughter and hasSon respectively.
This way, stating that A hasSon B and A hasDaughter B will cause an inconsistency.