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AlarmPP

Author: John Fitzgerald and Peter Gorm Larsen

This is the alarm example from the VDM++ book, John Fitzgerald, Peter Gorm Larsen, Paul Mukherjee, Nico Plat and Marcel Verhoef. Validated Designs for Object-oriented Systems, Springer, New York. 2005, ISBN 1-85233-881-4. The example is inspired by a subcomponent of a large alarm system developed by IFAD A/S. It is modelling the management of alarms for an industrial plant. The purpose of the model is to clarify the rules governing the duty roster and calling out of experts to deal with alarms. A comparable model of this example also exists in VDM-SL.

Properties Values
Language Version: vdm10
Entry point : new Test1().Run()

expert.vdmpp

              
class Expert

instance variables

quali : set1 of Qualification;
                            
types 
 
public Qualification = <Mech> | <Chem> | <Bio> | <Elec>;
                            
operations

public Expert: set1 of Qualification ==> Expert
Expert(qs) ==
  quali := qs;
                              
pure public GetQuali: () ==> set of Qualification
GetQuali() ==
  return quali;
  
end Expert

alarm.vdmpp

              
class Alarm
types
                            
types

public String = seq of char;

instance variables 

descr    : String;
reqQuali : Expert`Qualification;
                            
operations

public Alarm: Expert`Qualification * String ==> Alarm
Alarm(quali,str) ==
( descr := str;
  reqQuali := quali
);
                               
pure public GetReqQuali: () ==> Expert`Qualification
GetReqQuali() ==
  return reqQuali;
  
end Alarm

plant.vdmpp

              
class Plant

instance variables

alarms   : set of Alarm;
schedule : map Period to set of Expert;
inv PlantInv(alarms,schedule);

functions

PlantInv: set of Alarm * map Period to set of Expert -> 
          bool
PlantInv(as,sch) ==
  (forall p in set dom sch & sch(p) <> {}) and
  (forall a in set as &
     forall p in set dom sch &
       exists expert in set sch(p) &
         a.GetReqQuali() in set expert.GetQuali());

types

public Period = token;

operations

pure public ExpertToPage: Alarm * Period ==> Expert
ExpertToPage(a, p) ==
  let expert in set schedule(p) be st
      a.GetReqQuali() in set expert.GetQuali()
  in
    return expert
pre a in set alarms and
    p in set dom schedule
post let expert = RESULT
     in
       expert in set schedule(p) and
       a.GetReqQuali() in set expert.GetQuali();
                              
pure public NumberOfExperts: Period ==> nat
NumberOfExperts(p) ==
  return card schedule(p)
pre p in set dom schedule;

pure public ExpertIsOnDuty: Expert ==> set of Period
ExpertIsOnDuty(ex) ==
  return {p | p in set dom schedule & 
              ex in set schedule(p)};

public Plant: set of Alarm * 
              map Period to set of Expert ==> Plant
Plant(als,sch) ==
( alarms := als;
  schedule := sch
)
pre PlantInv(als,sch);

end Plant

test1.vdmpp

              
class Test1

instance variables

a1   : Alarm  := new Alarm(<Mech>,"Mechanical fault");
a2   : Alarm  := new Alarm(<Chem>,"Tank overflow");
ex1  : Expert := new Expert({<Mech>,<Bio>});
ex2  : Expert := new Expert({<Elec>});
ex3  : Expert := new Expert({<Chem>,<Bio>,<Mech>});
ex4  : Expert := new Expert({<Elec>,<Chem>});
plant: Plant  := new Plant({a1},{p1 |-> {ex1,ex4},
                                 p2 |-> {ex2,ex3}});

values

p1: Plant`Period = mk_token("Monday day");
p2: Plant`Period = mk_token("Monday night");
p3: Plant`Period = mk_token("Tuesday day");
p4: Plant`Period = mk_token("Tuesday night");

operations

pure public Run: () ==> set of Plant`Period * Expert
Run() == 
  let periods = plant.ExpertIsOnDuty(ex1),
      expert  = plant.ExpertToPage(a1,p1)
  in 
    return mk_(periods,expert);

end Test1