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Software Evolution

Swe04

Useful software is never a one shot development product. Rather over its lifetime new functions are added and it is adapted to new environments. 
In the words of [[http://www.doc.ic.ac.uk/~mml/][Lehman]]'s law: _A system that is used will be changed_.

Such extensions and adaptations should be done with care. 
Lehman's second laws states: 
_An evolving system increases its complexity, unless work is done to reduce it_.
[[Software maintenance]] is concerned with correcting existing defects and adding extensions,
while keeping complexity low.
Evolution of large systems requires a systematic approach to [[software understanding]],
since knowledge about the internals of a system evaporates over time.

Some links

   * [[http://www.doc.ic.ac.uk/~mml/feast/][FEAST]] project (Feedback, Evolution And Software Technology) of [[http://www.doc.ic.ac.uk/~mml/][Lehman]]

   * [[http://www.program-transformation.org/twiki/bin/view/Transform/SoftwareEvolution][Software Evolution]] at program-transformation.org