Conceptual Data Warehouse Design - Data Warehouse Systems: Design and Implementation - page 93

a

ATM Agency Branch Bank

ATMNumber
Address
Model
MoneyCapacity
...

AgencyName
Address
Area
NoEmployees
...

BranchName
Address
MinCapital
MaxCapital
...

BankName
Address
Manager
Headquarters
...

b

Bank bank X

Branch branch 1 branch 2 branch 3

Agency agency 11 agency 12 agency 31 agency 32

ATM ATM 111 ATM 112

Fig. 4.4 An unbalanced hierarchy. ( a )Schema.( b ) Examples of instances

Andrew
Fuller

Employee

Nancy
Davolio

Janet
Leverling

Margaret
Peacock

Steven
Buchanan

Laura
Callahan

Employee

Michael
Suyama

Robert
King

Anne
Dodsworth

Employee

Fig. 4.5 Instances of the parent-child hierarchy in the Northwind data warehouse

An example is given by dimension Employee in Fig. 4.2 , which represents an
organizational chart in terms of the employee-supervisor relationship. The
Subordinate and Supervisor roles of the parent-child relationship are linked
to the Employee level. As seen in Fig. 4.5 , this hierarchy is unbalanced since
employees with no subordinate will not have descendants in the instance tree.

4.2.3 Generalized Hierarchies

Sometimes, the members of a level are of different types. A typical example
arises with customers, which can be either companies or persons. Such