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Data on the history of seven systems was analysed to statistically test the 5 laws of software evolution proposed first by Belady and Lehman in 1976.While there was some evidence supporting laws 1 and 2, laws 3-5 were not supported by the data. In the light of the result a new discontinuous model of software evolution is proposed to replace the smoothly changing continuous model proposed by Lehman.
Michael Lawrence (Mon,) studied this question.