TU Wien:Einführung in wissensbasierte Systeme VU (Egly)/Übungen SS12/Blatt 3 - Beispiel 5

Let

• $T\,$ be a theory of classical (monotonic) logic
• $A\,$ a formula of classical logic
• ${\text{CWA}}(T)\,$ the Closed-World Assumption of $T\,$
• and $\models \,$ the consequence relation of the classical logic.

Furthermore, let $\models _{cwa}\,$ be the consequence relation defined as $T\models _{cwa}A\,$ iff ${\text{CWA}}(T)\models A\,$.

Give an example which shows that $\models _{cwa}\,$ does not satisfy the monotonicity principle.