ITIL v4 introduces with three explicit models:
ITIL v3 had a general concept of "good practices" but no codified rules. itil v3 vs v4
If you are starting fresh, choose ITIL v4 . If you are using v3, do not "rip and replace." Instead, adopt the Guiding Principles and the Value Streams approach to evolve your v3 environment. ITIL v4 introduces with three explicit models: ITIL