The ITIL 4 Service Value System (SVS) ties Guiding Principles, Governance, the
Service Value Chain, the management Practices, and Continual Improvement into one
operating model. The Service Value Chain has six activities — Plan,
Improve, Engage, Design & Transition,
Obtain / Build, Deliver & Support. A "value stream" in
ITIL 4 is just a path through these activities for a specific outcome.
Argitron makes the value chain visible: you can trace a customer-impacting outcome
from the strategic objective that funded it, through the project that built it, the
change that deployed it, the service that runs it, and the controls that govern it.