Software change - ESSeRE

Distribution Factors
F a c tor
B u sin ess im p or ta n ce
S ystem a g e
S ystem str u ctu r e
H a r d w a r e p r ocu r em en t
p olicies
D e sc r ip tion
R etu r n s on th e in vestm en t of d istr ibu tin g a leg a cy system d ep en d on its
im p or ta n ce to th e bu sin ess a n d h ow lon g it w ill rem a in im p orta n t. If
d istr ibu tion p r ovid es m or e efficien t su p p ort for sta ble bu sin ess p r ocesses
th en it is m or e lik ely to be a cost-effective evolu tion str a teg y.
T h e old er th e system th e m or e d ifficu lt it w ill be to m od ify its
a r ch itectu r e beca u se p r eviou s ch a n g es w ill h a ve d eg r a d ed th e str u ctu r e
of th e system .
T h e m or e m od u la r th e system , th e ea sier it w ill be to ch a n g e th e
a r ch itectu r e. If th e a p p lica tion log ic, th e d a ta m a n a g em en t a n d th e u ser
in terfa ce of th e system a r e closely in ter tw in ed , it w ill be d ifficu lt to
sep a ra te fu n ction s for m ig r a tion .
A p p lica tion d istr ibu tion m a y be n ecessa r y if th er e is com p a n y p olicy to
r ep la ce ex p en sive m a in fr a m e com p u ter s w ith ch ea p er server s. .
©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 21 Slide 34