To get a feel for object-oriented architectures, consider a very simple program designed to update the contents of a particular master file. Figure A-2.3.1 shows the “old” way of architecting such a program, by logical decomposition of the process into steps that are sequentially linked to produce the program. To produce this program, each element of the process must be coded in tightly-linked sequences.

By contrast, in the object-oriented architecture shown in Figure A-2.3.2, the program is divided into abstractions of the key elements. Instead of steps, the problem is now defined in terms of autonomous interconnected objects. Each object has its real-world mission defined, and is given its operational orders and required variables through the bus.

Program development using object-oriented technology can be divided into four interdependent elements.

• The first critical task is the definition of program requirements. This requires close communication with the intended users and an understanding of their applications.

• Program architecture is developed on the basis of these requirements. The skill of the architect determines the ultimate quality of the program and the time required to complete it.

• The production of the program proceeds, with coding by programmers who write within tight guidelines provided by the program architects.

• Finally, the completed program must be tested. Note that testing can account for between 40 and 50 percent of the cost of developing a large program.

Program definition and architecture require the most skilled and experienced people. These two steps produce virtually all of the program's intellectual property value.