Here are some key points about subset constraints:- A subset constraint specifies that the population of one role must be a subset of the population of another role. - It is used to model hierarchical or "is-a" relationships between roles.- A common example is an "Employee is-a Person" constraint, where the Employee role is a subset of the Person role.- Subset constraints help enforce integrity by ensuring all instances of one role are also instances of the other role.- They can be implied by other constraints like mandatory roles, so it's important to only specify explicit constraints.The example shown illustrates how a subset constraint may be redundant and unnecessary if it is already implied by another constraint like
Similaire à Here are some key points about subset constraints:- A subset constraint specifies that the population of one role must be a subset of the population of another role. - It is used to model hierarchical or "is-a" relationships between roles.- A common example is an "Employee is-a Person" constraint, where the Employee role is a subset of the Person role.- Subset constraints help enforce integrity by ensuring all instances of one role are also instances of the other role.- They can be implied by other constraints like mandatory roles, so it's important to only specify explicit constraints.The example shown illustrates how a subset constraint may be redundant and unnecessary if it is already implied by another constraint like
Similaire à Here are some key points about subset constraints:- A subset constraint specifies that the population of one role must be a subset of the population of another role. - It is used to model hierarchical or "is-a" relationships between roles.- A common example is an "Employee is-a Person" constraint, where the Employee role is a subset of the Person role.- Subset constraints help enforce integrity by ensuring all instances of one role are also instances of the other role.- They can be implied by other constraints like mandatory roles, so it's important to only specify explicit constraints.The example shown illustrates how a subset constraint may be redundant and unnecessary if it is already implied by another constraint like (20)
Here are some key points about subset constraints:- A subset constraint specifies that the population of one role must be a subset of the population of another role. - It is used to model hierarchical or "is-a" relationships between roles.- A common example is an "Employee is-a Person" constraint, where the Employee role is a subset of the Person role.- Subset constraints help enforce integrity by ensuring all instances of one role are also instances of the other role.- They can be implied by other constraints like mandatory roles, so it's important to only specify explicit constraints.The example shown illustrates how a subset constraint may be redundant and unnecessary if it is already implied by another constraint like