Strategy for legacy software system code redesign

Basically, process of redesign of old existing software system can be presented as following sequence:

1) Define goal for redesign, and characteristics of system after redesign.

2) Cover by tests and measurements to measure degree of correspondence to characteristics defined.

3) Define methods for improvements.

4) Do redesign by methods defined in 3, keeping 2nd) tests and measurements.

5) If 1) goal of redesign achieved stop.


Other things, that should be kept during redesign, if you want to keep system live long after redesign done:

http://rgritsulyak.blogspot.com/2009/03/survivable-long-living-systems.html