This chapter tackles the challenges of variability identification, modelling and implementation for service-based systems. The DiVA methodology is applied to the Mobile Phone Service Portability case-study to demonstrate its solutions to these challenges. The DiVA methodology utilises concepts of Aspect-Oriented Software Development to encapsulate service variants in distinct modules and uses Model- Driven Development techniques to analyse and transform conceptual designs into executable services. The DiVA approach provides a tool-supported methodology for managing dynamic variability in adaptive systems and taming system complexity.