Domain relational calculus
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
asked Dec 3 '18 at 19:07
EdmondEdmond
12
add a comment |
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
asked Dec 3 '18 at 19:07
EdmondEdmond
12
add a comment |
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
asked Dec 3 '18 at 19:07
EdmondEdmond
12
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
asked Dec 3 '18 at 19:07
EdmondEdmond
12
asked Dec 3 '18 at 19:07
EdmondEdmond
12
asked Dec 3 '18 at 19:07
EdmondEdmond
12
asked Dec 3 '18 at 19:07
EdmondEdmond
12
asked Dec 3 '18 at 19:07
EdmondEdmond
12
12
add a comment |
add a comment |
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