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    | • | SDL differentiates between process definition and 
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    |  | process
    instance 
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    | • | Defined
    process activation mechanism 
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    |  | 
   
    | • | Receiver
    process instance 
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    |  | 
   
    | (1 receiverprocess start 
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    |  | 
   
    | ((ackid . nil) (frameid . nil) (self .
    1) 
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    | (sender . nil)
    (parent . 0) (offspring . nil) 
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    |  | 
   
    | ((start …)) nil) 
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    | • | Correctness property: defined a recognizer for 
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    |  | valid
    instances of a system 
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    |  | 
   
    | (defthm activate-makes-instance 
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    | (implies (wf-type S) 
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    |  | 
   
    | (wf-instance
    (activate S) S))) 
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