update in this scenario, two satellites, Unit A and Unit B, orbit around Mars; the satellites are programmed to land while transmitting their status to Earth;  Earth has received a transmission from one of the satellites, communicating that it is still in orbit ; however , due to interference, it is not known which satellite sent the signal; subsequently, Earth receives the communication that Unit A has landed ; this scenario can be modeled in the following way ; two propositional variables and indicate that Unit A and Unit B, respectively, are still in orbit; the initial set of beliefs is (either one of the two satellites is still in orbit) and the new piece of information is (Unit A has landed, and is therefore not in orbit) ; the only rational result of the update is ; since the initial information that one of the two satellites had not landed yet was possibly coming from the Unit A, the position of the Unit B is not known ; revision the play "Six Characters in Search of an Author" will be performed in one of the two local theatres ; this information can be denoted by , where and indicates that the play will be performed at the first or at the second theatre, respectively; a further information that "Jesus Christ Superstar" will be performed at the first theatre indicates that holds ; in this case, the obvious conclusion is that "Six Characters in Search of an Author" will be performed at the second but not the first theatre, which is represented in logic by .
update in this scenario, two satellites, Unit A and Unit B, orbit around Mars; the satellites are programmed to land while transmitting their status to Earth; and Earth has received a transmission from one of the satellites, communicating that it is still in orbit . However , due to interference, it is not known which satellite sent the signal; subsequently, Earth receives the communication that Unit A has landed . This scenario can be modeled in the following way : two propositional variables and indicate that Unit A and Unit B, respectively, are still in orbit; the initial set of beliefs is (either one of the two satellites is still in orbit) and the new piece of information is (Unit A has landed, and is therefore not in orbit) . The only rational result of the update is ; since the initial information that one of the two satellites had not landed yet was possibly coming from the Unit A, the position of the Unit B is not known . revision the play "Six Characters in Search of an Author" will be performed in one of the two local theatres . This information can be denoted by , where and indicates that the play will be performed at the first or at the second theatre, respectively; a further information that "Jesus Christ Superstar" will be performed at the first theatre indicates that holds . In this case, the obvious conclusion is that "Six Characters in Search of an Author" will be performed at the second but not the first theatre, which is represented in logic by .
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