At least 80 percent of the costs incurred for any computer system are incurred postdelivery. An error detected during testing costs four times as much to correct as one caught at specification stage. (From Software Engineering Economics, by Barry W. Boehm (Prentice-Hall, 1981).) How much does an error detected during production running cost? How much more an error that is never detected? Like the classic “lemon” car first off the line on Monday or the last one off on Friday, some of our rapidly developed systems seem to spend more time being fixed than “on the road.”
Finally, failure in any or all of the above aspects indicates the presence of DDS. These symptoms are to be taken only as indicative and not prescriptive.