| 0 |      1 | (*  Title: 	91/Modal/T
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|  |      2 |     ID:         $Id$
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|  |      3 |     Author: 	Martin Coen
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|  |      4 |     Copyright   1991  University of Cambridge
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|  |      5 | *)
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|  |      6 | 
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|  |      7 | T = Modal0 +
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|  |      8 | rules
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|  |      9 | (* Definition of the star operation using a set of Horn clauses *)
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|  |     10 | (* For system T:  gamma * == {P | []P : gamma}                  *)
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|  |     11 | (*                delta * == {P | <>P : delta}                  *)
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|  |     12 | 
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|  |     13 |   lstar0         "|L>"
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|  |     14 |   lstar1         "$G |L> $H ==> []P, $G |L> P, $H"
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|  |     15 |   lstar2         "$G |L> $H ==>   P, $G |L>    $H"
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|  |     16 |   rstar0         "|R>"
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|  |     17 |   rstar1         "$G |R> $H ==> <>P, $G |R> P, $H"
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|  |     18 |   rstar2         "$G |R> $H ==>   P, $G |R>    $H"
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|  |     19 | 
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|  |     20 | (* Rules for [] and <> *)
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|  |     21 | 
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|  |     22 |   boxR
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|  |     23 |    "[| $E |L> $E';  $F |R> $F';  $G |R> $G';  \
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|  |     24 | \               $E'        |- $F', P, $G'|] ==> $E          |- $F, []P, $G"
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|  |     25 |   boxL     "$E, P, $F  |-         $G    ==> $E, []P, $F |-          $G"
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|  |     26 |   diaR     "$E         |- $F, P,  $G    ==> $E          |- $F, <>P, $G"
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|  |     27 |   diaL
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|  |     28 |    "[| $E |L> $E';  $F |L> $F';  $G |R> $G';  \
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|  |     29 | \               $E', P, $F'|-         $G'|] ==> $E, <>P, $F |-          $G"
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|  |     30 | end
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