Software will always evolve

or it will die out

Modern software systems are large, highly complex built on top of other systems leading to large conglomerated systems of systems. Consider the graph visualization on the right, it shows the traceability network, visualized using an organic layout and it represents traceability relations between (about) 4,000 artifact. The challenge is, given a large software intensive system with the complex relations between elements, how can we make changes without risking disrupting expected behavior? How can changes be made in a cost effective way ?