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Prove that:

Two finite rooted frames are isomorphic iff they validate the same formulas.

(This is an exercise in the book "Modal Logic" by A.Chagrov and M.Zakharyaschev)

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    What kind of frames, what kind of formulas are we talking about? Do we have one modality (one relation on frames)? Are reflexivity and/or transitivity (S4) assumed?2012-10-08
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    @Berci . The language of intuitionistc propositional logic is same as the language of classical propositional logic. And the frames are all partial ordered frames.2012-10-08
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    Ah, sorry, this booktitle "Modal Logic" misled me... So, then.. what is a 'rooted frame' and the semantics?2012-10-08
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    @Berci . See the item "Semantics of intuitionistic logic" in the following website: http://en.wikipedia.org/wiki/Kripke_semantics2012-10-08
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    To understand the question, it is important to know that the definition of "rooted frame" is that every node is accessible from the "root" with one or more steps. So "rooted" does not just mean "pointed" as might be expected; "rooted" affects both the order structure of the frame and the choice of a root node.2013-07-22

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