The ITIL service lifecycle stages are interconnected and ensure that services remain aligned with business needs.

• Service Strategy defines the direction and sets priorities, financial models, and risk management approaches. These guide Service Design, Service Transition, Service Operation, and Continual Service Improvement.
• Service Design provides detailed specifications that enable Service Transition to deploy services effectively. It includes clear architectures, security policies, and capacity plans that support integration.
• Service Transition moves services into operation and depends on Service Design outputs. It manages risks and provides feedback that informs both Service Design refinements and Continual Service Improvement initiatives
• Service Operation maintains live services and delivers performance data to Continual Service Improvement. This ensures that services remain relevant and efficient.
• Continual Service Improvement analyses data from all lifecycle stages and recommends changes to Service Strategy, Service Design, Service Transition, and Service Operation. These changes help optimise service quality.

Figure 1 illustrates these interdependencies, showing how each stage contributes to a cohesive service lifecycle.