Domain relational calculus











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There are 2 relations:



Prediction(cname, etype)



Measures(etype, provider)



cname - city name of predicted future disaster.



etype - event type. earthquake, tsunami...



provider - police, ambulance...



I need to write a query using domain relational calculus and it should find a provider that provides service to all predicted events in Milano.



I have this so far:



{<P> | ∃et <et,P> ∈ Measures ^ ∀ ev (<'Milano', ev> ∈ Prediction 

⟹  ∃pr(ev,pr) ^ pr=P)}


I am not sure about it. Is it ok? or something is wrong?






relations relation-algebra







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    up vote
    0
    down vote

    favorite












    There are 2 relations:



    Prediction(cname, etype)



    Measures(etype, provider)



    cname - city name of predicted future disaster.



    etype - event type. earthquake, tsunami...



    provider - police, ambulance...



    I need to write a query using domain relational calculus and it should find a provider that provides service to all predicted events in Milano.



    I have this so far:



    {<P> | ∃et <et,P> ∈ Measures ^ ∀ ev (<'Milano', ev> ∈ Prediction 
    
⟹  ∃pr(ev,pr) ^ pr=P)}


    I am not sure about it. Is it ok? or something is wrong?






    relations relation-algebra







    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      There are 2 relations:



      Prediction(cname, etype)



      Measures(etype, provider)



      cname - city name of predicted future disaster.



      etype - event type. earthquake, tsunami...



      provider - police, ambulance...



      I need to write a query using domain relational calculus and it should find a provider that provides service to all predicted events in Milano.



      I have this so far:



      {<P> | ∃et <et,P> ∈ Measures ^ ∀ ev (<'Milano', ev> ∈ Prediction 
      
⟹  ∃pr(ev,pr) ^ pr=P)}


      I am not sure about it. Is it ok? or something is wrong?






      relations relation-algebra







      share|cite|improve this question













      There are 2 relations:



      Prediction(cname, etype)



      Measures(etype, provider)



      cname - city name of predicted future disaster.



      etype - event type. earthquake, tsunami...



      provider - police, ambulance...



      I need to write a query using domain relational calculus and it should find a provider that provides service to all predicted events in Milano.



      I have this so far:



      {<P> | ∃et <et,P> ∈ Measures ^ ∀ ev (<'Milano', ev> ∈ Prediction 
      
⟹  ∃pr(ev,pr) ^ pr=P)}


      I am not sure about it. Is it ok? or something is wrong?






      relations relation-algebra




      relations relation-algebra






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Dec 3 at 19:07









      Edmond

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