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    | • | Other
    approaches to verification of SDL 
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    |  | specifications are based on model checkers. 
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    |  | A
    couple of examples 
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    |  | 
   
    |  | – | IF
    system from Verimag converts SDL to 
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    |  | PROMELA
    and uses SPIN model checker 
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    |  | 
   
    |  | – | A
    proprietary verification system at Siemens 
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    |  | relies
    on a BDD-based symbolic checker 
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