Relative model of the logical entropy of sub--algebras

‎In the context of observers‎, ‎any mathematical model according to the viewpoint of an observer is called a relative model‎. ‎The purpose of the present paper is to study the relative model of logical entropy‎. ‎Given an observer ‎, ‎we define the relative logical entropy and relative conditional logical entropy of a sub- -algebra having finitely many atoms on the relative probability ‎‎ measure space and prove the ergodic properties of these measures‎. ‎Finally‎, ‎it is shown that the relative logical entropy is invariant under‎ ‎the relation of equivalence modulo zero.