This work is based on a retrospective analysis of a renewal process applied
to a very aged, highly degraded software system. Some parts of the results
are generalized to define a method for determining the technical and econo
mic qualities of software system components. The work also presents a decis
ion model for identifying the most suitable renewal process to be applied,
based on the quality of the components and the aims of the renewal process.
With the model presented, decision-making on the renewal process is specia
lized to each component of the software system, thus ensuring greater benef
its from the process as a whole. The same model can be used to monitor soft
ware system quality decay and thus avoid the need to use the most costly re
newal processes.