This chapter is from the book
Figure 1.3 portrays what happens when an application invokes operationA on a ConcreteDataAccessor.
The ConcreteDataAccessor implements
the logical operation in terms of one or more physical operations. It is also likely to interpret or convert the input and
output data as well as handle physical resource management on the application's behalf.
Figure 1.3. An application invokes operationA on a ConcreteDataAccessor.