This chapter covers the elements of Ada added (in Ada 95) to provide better support for the classification style of OOD and OOP. These elements include tagged types, classwide types, classwide operations and dispatching operations.
The major advantages of the techniques about to be introduced relate to more opportunities for reuse of software modules, reduced demands for testing, and less copying and re-compiling. These advantages flow from the use of inheritance. The reader is cautioned, however, that inheritance can be over-used or mis-used. A deep inheritance hierarchy can result in code that is hard to understand, because one must grasp the entire hierarchy in order to understand a single low-level module. See also, the discussion in the next section of "is a" versus "has a" relationships between elements of a hierarchy.
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